Electronic mail transmission system

Abstract

To provide an electronic mail transmission system which safely transmits an attached file and in which interruption of electronic mail does not occur.SOLUTION: When an attached file is attached to transmission mail, a transmission-side mail server 3 included in an electronic mail transmission system 2 confirms whether or not a destination-side mail server 7 is adapted to TLS communications. In a case where it is adapted to TLS, the transmission mail including the attached file is sent to the destination-side mail server 7 via an encrypted communication path which is encrypted by TLS. In a case where the destination-side mail server 7 is not adapted to TLS, on the other hand, the attached file separated from the transmission mail is sent toward an attached file storage server 4, and the attached file is provided from the attached file storage server 4 or the separated attached file is compressed into a compression file with a password, attached to the transmission mail again and sent to the destination-side mail server 7 via a non-encrypted communication path which is not encrypted by TLS.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electronic mail transmission system including a sending mail server that sends out an outgoing mail created at a sender's terminal to a destination mail server. [Background technology]

[0002] In previous e-mail systems, the communication path between mail servers was not encrypted, and plain text e-mails were sent. Since files attached to e-mails may contain highly confidential information, in an attempt to reduce the risk of attachments being intercepted, the attachments are compressed into password-protected ZIP encrypted files, and this ZIP file is attached to the outgoing e-mail. After sending an e-mail with a ZIP encrypted file attached, the sender creates another e-mail containing the password to unzip the ZIP encrypted file and sends it to the same destination.

[0003] According to a survey conducted by the inventor, it has been confirmed that approximately 90% of communication paths between mail servers are encrypted today. For encryption between mail servers, a protocol that provides highly secure communication, such as TLS (Transport Layer Security), is used.

[0004] Several e-mail systems have been proposed to date that utilize the fact that communication paths between mail servers are encrypted. For example, the e-mail server device described in Patent Document 1 below is known.

[0005] This e-mail server device determines whether communication with the destination mail server is possible using a secure communication procedure such as SSL (Secure Socket Layer) or TLS, and delivers e-mail using a secure communication procedure if communication is possible. On the other hand, if communication with the destination mail server using a secure procedure is not possible, the e-mail server device either delivers the e-mail as is or stops delivery. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2006-345403 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the e-mail server device described in Patent Document 1, if communication using secure communication procedures is not possible, the e-mail is delivered without using secure communication procedures, which creates a risk of eavesdropping. In addition, if delivery is stopped when communication using secure communication procedures is not possible, e-mail communication is cut off, which makes the device less user-friendly.

[0008] Because attachments often contain more confidential information than the main text of an e-mail, there was a demand for an easy-to-use e-mail transmission system that could send attachments securely and prevent e-mail delivery interruptions.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an e-mail transmission system that can transmit attachments safely and that does not cause interruptions in e-mail delivery. [Means for solving the problem]

[0010] In order to solve the above problem, the invention described in claim 1 is an electronic mail transmission system including a sending mail server that sends an outgoing mail created by a sender terminal to a destination mail server, the sending mail server including an outgoing mail reception unit that receives the created outgoing mail from the sender terminal, an attachment detection unit that detects whether or not the accepted outgoing mail has an attachment, an encrypted communication compatibility information inquiry unit that obtains encrypted communication compatibility information including information on whether or not the destination mail server of the outgoing mail supports encrypted communication from the destination mail server, an attachment separation unit that separates the attachment from the outgoing mail and divides it into the attachment and the outgoing mail from which the attachment has been removed, an outgoing mail sending setting storage unit that stores in advance settings for a method of sending the attachment when the destination mail server does not support encrypted communication, an outgoing mail sending unit that sends the outgoing mail to the destination mail server, and and an encrypted communication determination process control unit that controls the sending operation of the outgoing mail based on response information, and when the attachment detection unit detects that the outgoing mail has an attachment, the encrypted communication determination process control unit causes the encrypted communication compatibility information inquiry unit to acquire the encrypted communication compatibility information of the destination mail server, and when it is confirmed from the acquired encrypted communication compatibility information that the destination mail server is compatible with the encrypted communication, causes the encrypted communication determination process control unit to select an encrypted communication path encrypted by the encrypted communication and send the outgoing mail including the attachment to the outgoing mail sending unit toward the destination mail server, and when it is confirmed that the destination mail server does not support the encrypted communication, causes the attachment separated from the outgoing mail by the attachment separation unit based on the setting of the outgoing mail sending setting storage unit, and causes the outgoing mail from which the attachment has been removed to be sent to the outgoing mail sending unit toward the destination mail server through a non-encrypted communication path that is not encrypted by the encrypted communication.

[0011] The invention according to claim 2, in addition to the configuration according to claim 1, further comprises an attachment storage server that stores the attachment and provides the stored attachment in response to a request for providing the attachment, the attachment storage server having an attachment reception unit that receives the attachment sent from the sending mail server, an attachment storage unit that stores the received attachment, an attachment provision request reception unit that receives the request for providing the attachment stored in the attachment storage unit, and an attachment provision unit that provides the attachment to a request source that sent the request for providing, the sending mail server having an attachment upload unit that sends the attachment to the attachment storage server, the sending mail server further having a compression / decompression password generation unit that generates a compression / decompression password that is applied to encryption / compression conversion for compressing the attachment into a password-protected compressed file and is also applied to decryption / decompression conversion for decompressing the password-protected compressed file into the attachment before compression, and a compression / decompression password generation unit that generates a compression / decompression password that is applied to encryption / compression conversion for compressing the attachment into a password-protected compressed file and is also applied to decryption / decompression conversion for decompressing the password-protected compressed file into the attachment before compression, and a compressed file re-attaching unit which re-attaches the password-protected compressed file created by the attachment compression unit to the outgoing mail from which the attachment has been removed, wherein the attachment storage server receives the attachment sent from the attachment upload unit in the attachment reception unit, stores the received attachment in the attachment storage unit, and when the attachment provision request reception unit receives the provision request for the attachment, the attachment provision unit provides the attachment to the requester which sent the provision request. The sending mail server has an attachment compression unit which applies the compression and decompression password generated by the compression and decompression password generation unit to the attachment separated by the attachment separation unit to create the password-protected compressed file, and the compressed file re-attaching unit re-attaches the created password-protected compressed file to the outgoing mail from which the attachment has been removed,The outgoing mail to which the password-protected compressed file is attached is sent from the outgoing mail sending unit to the destination mail server through the unencrypted communication path, and the method of sending the attachment set in the outgoing mail sending setting holding unit is set selectably to either send the attachment separated by the attachment separation unit from the attachment upload unit to the attachment storage server, or compress the attachment separated by the attachment separation unit into the password-protected compressed file and send the outgoing mail to which the password-protected compressed file is attached from the outgoing mail sending unit to the destination mail server.

[0012] The invention of claim 3 has the configuration as described in claim 2, and is characterized in that the outgoing mail sending setting storage unit is also pre-set with a method for sending the outgoing mail from which the attachment has been removed, and when it is confirmed that the destination mail server does not support the encrypted communication, the encrypted communication determination processing control unit causes the outgoing mail from which the attachment has been removed by the attachment separation unit to be sent from the outgoing mail sending unit based on the setting of the outgoing mail sending setting storage unit, and the method for sending the outgoing mail from which the attachment has been removed, which is set in the outgoing mail sending setting storage unit, is selectable from among holding the outgoing mail for a predetermined period of time and sending the outgoing mail after the predetermined period of time has elapsed, adding a predetermined email address to a blind carbon copy of the outgoing mail and then sending the outgoing mail, canceling the sending of the outgoing mail, sending the outgoing mail after approval by a predetermined approver, sending the outgoing mail and notifying a pre-registered email address, or sending the outgoing mail immediately.

[0013] The invention of claim 4 is characterized in that, in addition to the configuration described in claim 2 or 3, the sending mail server has an sending mail body appending unit that adds text to the body of the sending mail, and the encrypted communication determination processing control unit controls the sending mail body appending unit to add text indicating whether the destination mail server supports the encrypted communication to the body of the sending mail, based on the encrypted communication compatibility information of the destination mail server acquired by the encrypted communication compatibility information inquiry unit.

[0014] The invention of claim 5 is characterized in that, in addition to the configuration described in claim 4, the sending mail server has a sender terminal notification unit that notifies the sender terminal that sent the outgoing email, and the encrypted communication determination processing control unit controls the sender terminal notification unit to notify the sender terminal of information indicating whether the outgoing email has been sent to the destination mail server via the encrypted communication path.

[0015] The invention of claim 6 is characterized in that, in addition to the configuration described in claim 5, an administrator terminal that manages the email sending status of the sender terminal is communicatively connected to the sending mail server, the sending mail server has an administrator terminal notification unit that notifies the administrator terminal of the sending result of the outgoing mail sent from the sender terminal, and the encrypted communication determination processing control unit controls the administrator terminal notification unit to notify the administrator terminal notification unit of information indicating whether the outgoing mail has been sent to the destination mail server via the encrypted communication path.

[0016] The invention of claim 7, in addition to the configuration described in claim 6, is characterized in that the sending mail server has a sent mail history memory unit that stores, for each sent mail sent from the sender terminal, information on whether the sent mail has been sent to the destination mail server through the encrypted communication path, sending history information including sender information and destination information, a sent mail history report creation unit that creates a sent mail history report based on the sending history information of the multiple sent mails stored in the sent mail history memory unit, and a sent mail history report providing unit that provides the sent mail history report created by the sent mail history report creation unit, and the sent mail history report includes personal data that is the number of encrypted communication mails, which is the number of sent mails sent to the destination mail server through the encrypted communication path, the number of unencrypted communication mails, which is the number of sent mails sent through the unencrypted communication path, and the ratio of the number of encrypted communication mails and the number of unencrypted communication mails to the total number of sent mails, compiled for each sender and / or destination, or statistical information data that is compiled for the personal data of multiple senders and / or multiple destinations.

[0017] The invention of claim 8 is characterized in that, in addition to the configuration described in claim 4, the sending mail server has a pseudo screen creation unit that creates a pseudo display screen in which the sending mail body appending unit adds text to the body of the sending mail, and a pseudo screen providing unit that provides the pseudo screen of the sending mail created by the pseudo screen creation unit, and is able to create the pseudo screen of the sending mail when the destination mail server supports the encrypted communication and the sending mail is sent through the encrypted communication path, and the pseudo screen of the sending mail when the destination mail server does not support the encrypted communication and the sending mail is sent through the unencrypted communication path, regardless of the sending of the sending mail.

[0018] The invention according to claim 9 is an electronic mail transmission system including a sending mail server which sends an outgoing mail created on a sender terminal to a destination mail server, the sending mail server having an outgoing mail reception unit which receives the created outgoing mail from the sender terminal, an encrypted communication compatibility information inquiry unit which obtains encrypted communication compatibility information from the destination mail server including information on whether the destination mail server of the outgoing mail supports encrypted communication or not, an outgoing mail sending setting storage unit which stores in advance settings for a sending method of the outgoing mail when the destination mail server does not support encrypted communication, an outgoing mail sending unit which sends the outgoing mail to the destination mail server, and an encrypted communication determination process control unit which controls a sending operation of the outgoing mail based on the encrypted communication compatibility information obtained by the encrypted communication compatibility information inquiry unit, the encrypted communication determination process control unit being: The encrypted communication compatibility information inquiry unit is made to obtain the encrypted communication compatibility information of the destination mail server, and when it is confirmed from the obtained encrypted communication compatibility information that the destination mail server is compatible with the encrypted communication, an encrypted communication path encrypted by the encrypted communication is selected and the outgoing mail is sent to the outgoing mail sending unit toward the destination mail server, and when it is confirmed that the destination mail server does not support the encrypted communication, the outgoing mail is sent to the outgoing mail sending unit through a non-encrypted communication path that is not encrypted by the encrypted communication based on the setting of the outgoing mail sending setting storage unit.

[0019] The invention of claim 10 is characterized in that, in addition to the configuration described in claim 9, the method of sending the outgoing mail set in the outgoing mail sending setting storage unit is set to be selectable from among holding the outgoing mail for a predetermined time and sending the outgoing mail after the predetermined time has elapsed, adding a predetermined email address to a blind carbon copy of the outgoing mail and then sending the outgoing mail, canceling the sending of the outgoing mail, sending the outgoing mail after approval by a predetermined approver, sending the outgoing mail and notifying a previously registered email address, or sending the outgoing mail immediately. Effect of the Invention

[0020] According to the invention of claim 1, when it is confirmed that the destination mail server supports encrypted communication, the outgoing mail including the attachment is sent to the destination mail server by selecting the encrypted communication path encrypted by the encrypted communication, and on the other hand, when it is confirmed that the destination mail server does not support encrypted communication, the attachment is sent based on the setting of the outgoing mail sending setting storage unit, and the outgoing mail with the attachment removed is sent to the destination mail server through the non-encrypted communication path that is not encrypted by the encrypted communication. In this way, an email sending system that safely sends attachments and does not cause email interruptions is realized.

[0021] According to the invention of claim 2, when the destination mail server does not support encrypted communication, the method of sending the attachment is either to send the attachment to an attachment storage server and provide the attachment via the attachment storage server, or to compress the attachment into a password protected compressed file, attach the password protected compressed file to an outgoing mail, and send it to the destination mail server. This allows the attachment to be sent safely. A higher level of safety is ensured with the sending method using an attachment storage server. On the other hand, the method of attaching a password protected compressed file to an outgoing mail and sending it to the destination mail server does not require the installation of an attachment storage server, and the system configuration can be simplified.

[0022] According to the invention of claim 2, when the destination mail server does not support encrypted communication, the method of sending the attachment can be selected from either sending the attachment to an attachment storage server and providing the attachment via the attachment storage server, or compressing the attachment into a password protected compressed file, attaching the password protected compressed file to an outgoing mail and sending it to the destination mail server. This makes it easy to set the method of sending the attachment, and realizes a system that is easy to introduce and easy to use.

[0023] According to the invention of claim 3, there are multiple methods for sending outgoing mail with attachments removed when the destination mail server does not support encrypted communication, and various settings are possible. In addition, settings can be flexibly realized according to the needs of the user.

[0024] According to the invention of claim 3, the sending method of the outgoing mail from which the attachments have been removed when the destination mail server does not support encrypted communication can be selected from among multiple options. This makes it easy to set the sending method, and realizes a system that is easy to introduce and easy to use.

[0025] According to the invention of claim 4, a sentence indicating whether or not the destination mail server supports encrypted communication is added to the body of the outgoing email, so that when you receive an outgoing email, you can check whether the email was sent through an encrypted communication path that is encrypted by encrypted communication.

[0026] According to the invention of claim 5, it is possible to confirm at the sender's terminal of the outgoing mail whether the outgoing mail has been sent through an encrypted communication path that has been encrypted by encrypted communication.

[0027] According to the invention of claim 6, it is possible to check at the administrator terminal whether or not an outgoing email has been sent through an encrypted communication path.

[0028] According to the invention of claim 7, by checking the created sent mail history report, it is possible to perform a detailed analysis of the history, such as how many sent mails were sent through the encrypted communication path.

[0029] According to the invention of claim 8, the display screen of the outgoing mail to be delivered to the destination can be checked in advance.

[0030] According to the invention of claim 9, when it is confirmed that the destination mail server supports encrypted communication, the outgoing mail is sent to the destination mail server by selecting the encrypted communication path encrypted by the encrypted communication, and on the other hand, when it is confirmed that the destination mail server does not support encrypted communication, the outgoing mail is sent to the destination mail server through the non-encrypted communication path that is not encrypted by encrypted communication based on the setting of the outgoing mail sending setting storage unit. In this way, when the destination mail server supports encrypted communication, the outgoing mail is sent safely by encrypted communication, and when the destination mail server does not support encrypted communication, the outgoing mail is sent by the sending method set in advance. Therefore, the sender or administrator of the outgoing mail can know in advance the safety when the destination mail server does not support encrypted communication. In addition, an e-mail sending system in which e-mails are not interrupted can be realized.

[0031] According to the invention of claim 10, there are multiple methods for sending outgoing mail when the destination mail server does not support encrypted communication, and various settings are possible. In addition, settings can be flexibly realized according to the needs of users such as senders and administrators of outgoing mail.

[0032] According to the invention of claim 10, the sending method of the outgoing mail when the destination mail server does not support encrypted communication can be selected from multiple options. This makes it easy to set the sending method, and realizes a system that is easy to introduce and easy to use. [Brief description of the drawings]

[0033] [Figure 1] 1 is a configuration block diagram showing in outline a configuration of an electronic mail system including an electronic mail transmission system in accordance with embodiment 1 of the present invention. [Diagram 2] 2 is a schematic functional block diagram of a sending mail server included in the email sending system according to the first embodiment. FIG. [Diagram 3] 3 is a schematic diagram of an outgoing mail sending setting screen provided by the email sending system in accordance with the first embodiment. FIG. [Figure 4] 1A and 1B are schematic diagrams showing examples of the display screen of an email displayed to a recipient by the email sending system of embodiment 1, in which (a) shows the screen of an email sent via an unencrypted communication path that is not encrypted by TLS communication, and (b) shows the screen of an email sent via an encrypted communication path that is encrypted by TLS communication. [Diagram 5] 2 is a schematic functional block diagram of an attachment storage server included in the email transmission system according to the first embodiment. FIG. [Figure 6] FIG. 1 is a schematic diagram showing a flow of sending an e-mail in an e-mail system including the e-mail sending system according to the first embodiment, however, it shows a flow of sending an attachment to an attachment storage server when a destination mail server does not support TLS. [Figure 7] FIG. 1 is a schematic diagram showing a flow of sending an e-mail in an e-mail system including the e-mail sending system according to the embodiment 1. However, in the case where the destination mail server does not support TLS, the attached file is compressed into a password-protected compressed file, and the compressed file is attached to the outgoing e-mail and sent to the destination mail server. [Figure 8] FIG. 11 is a configuration block diagram showing in outline a configuration of an electronic mail system including an electronic mail transmission system in accordance with embodiment 2 of the present invention. [Figure 9] FIG. 11 is a schematic functional block diagram of a sending mail server included in the email sending system according to the second embodiment. [Figure 10] 11 is a schematic diagram showing a flow of sending an e-mail in an e-mail system including the e-mail sending system according to the second embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] [First embodiment of the invention] A first embodiment of the present invention will be described with reference to FIGS. 1 to 7. FIG.

[0035] FIG. 1 is a configuration block diagram that shows in outline an electronic mail system 1 including an electronic mail transmission system 2 according to a first embodiment of the present invention.

[0036] In this electronic mail system 1, a sending mail server 3, an attachment storage server 4, and a destination mail server 7 are connected via a communication line 9 such as the Internet. A sender terminal 5 from which a created outgoing mail is sent, and an administrator terminal 6 that manages the e-mail sending status of the sender terminal 5 are communicatively connected to the sending mail server 3. A destination terminal 8 that is the destination of the outgoing mail is communicatively connected to the destination mail server 7. The destination terminal 8 is also connected to the communication line 9, and is capable of downloading files stored in the attachment storage server 4 via the communication line 9.

[0037] Server devices are used for the sending mail server 3, the attachment storage server 4, and the destination mail server 7. Information terminals such as PCs (Personal Computers), smartphones, and tablets are used for the sender terminal 5, the administrator terminal 6, and the destination terminal 8, and each includes a CPU (Central Processing Unit), an auxiliary storage device which is a non-volatile storage device, a control unit including a RAM (Random Access Memory), a display unit, an input unit, and the like (not shown).

[0038] Moreover, the electronic mail transmission system 2 is configured to include a sending mail server 3 and an attachment file storage server 4 .

[0039] When a sending mail server 3 included in the electronic mail transmission system 2 accepts an outgoing mail created by a sender terminal 5, it sends the accepted outgoing mail to a destination mail server 7. The destination mail server 7 accepts and stores the outgoing mail, and provides the outgoing mail to the destination terminal 8 in response to a request from the destination terminal 8.

[0040] The sending mail server 3 detects whether or not an attachment is attached to the outgoing mail, and if it detects that an attachment is attached, it queries the destination mail server 7 of the outgoing mail to obtain encrypted communication support information including whether or not the destination mail server 7 supports encrypted communication. The "encrypted communication" may be any encrypted communication protocol such as SSL or TLS, but the following explanation will be given taking TLS as an example of "encrypted communication".

[0041] If it is confirmed from the acquired encrypted communication support information that the destination mail server 7 supports TLS communication, the outgoing mail including the attachment is sent from the sending mail server 3 to the destination mail server 7 through an encrypted communication path encrypted based on TLS. On the other hand, if it is confirmed that the destination mail server 7 does not support TLS communication, the attachment separated from the outgoing mail is sent by a sending method preset in the outgoing mail sending setting holding unit 304 of the sending mail server 3, and the outgoing mail with the attachment removed is sent to the destination mail server 7 through a non-encrypted communication path that is not encrypted by TLS.

[0042] The sending method of the attached file set in the outgoing mail sending setting holding unit 304 includes a method of sending the attached file to the attachment file storage server 4 and providing the attached file via this attachment file storage server 4, or a method of encrypting and compressing the attached file into a password-protected compressed file, reattaching this password-protected compressed file to the outgoing mail, and sending it to the destination mail server 7 through a non-encrypted communication path that is not encrypted by TLS. For example, a password-protected ZIP compressed file can be used as the password-protected compressed file.

[0043] In the sending method using the attachment storage server 4, the attachment sent from the sending mail server 3 is accepted by the attachment storage server 4, and the accepted attachment is stored. After that, when a request to provide the attachment is sent from the destination terminal 8 and accepted by the attachment storage server 4, the attachment storage server 4 provides the attachment to the destination terminal 8, which is the requester that sent the provision request.

[0044] In the sending method of reattaching a password-protected compressed file to an outgoing mail, first, a compression / decompression password that is applied to the encryption / compression conversion that compresses the attached file into a password-protected compressed file is generated in the sending mail server 3. This compression / decompression password is also applied to the decryption / decompression conversion that decompresses the password-protected compressed file into the attachment file before compression.

[0045] Next, the generated compression / decompression password is applied to the attachment separated from the outgoing mail to create a password-protected compressed file, and this password-protected compressed file is attached again to the outgoing mail from which the attachment was removed. After that, the outgoing mail with the password-protected compressed file attached is sent to the destination mail server 7 through a non-encrypted communication path that is not encrypted by TLS.

[0046] If the destination mail server 7 supports TLS communication, the sender mail server 3 can safely send the outgoing mail including the attachment to the destination mail server 7 via an encrypted communication path encrypted by TLS communication.

[0047] On the other hand, if the destination mail server 7 does not support TLS communication, the sender mail server 3 sends the attachment separated from the outgoing mail to the attachment storage server 4, and the attachment is provided safely from the attachment storage server 4. Alternatively, the attachment is encrypted into a password-protected compressed file and safely sent.

[0048] Attachments can be sent more securely in a method of sending the attachment to the attachment storage server 4 and providing the attachment from this attachment storage server 4. On the other hand, in a method of compressing the attachment into a password protected compressed file and reattaching it to the outgoing email, there is no need to install the attachment storage server 4, and the system configuration can be simplified.

[0049] Furthermore, even if the destination mail server 7 does not support TLS communication, the outgoing mail from which the attachment has been removed is sent to the destination mail server 7, so that the e-mail will not be blocked.

[0050] 2 is a schematic functional block diagram of the sending mail server 3. This sending mail server 3 is configured to include a control unit 30, an outgoing mail reception unit 32, a destination detection unit 34, an outgoing mail sending unit 36, a communication unit 38, and a TLS communication determination processing unit 300 as an "encrypted communication determination processing unit."

[0051] The control unit 30 is configured to include a CPU (not shown), an auxiliary storage device which is a non-volatile storage device, and a RAM. The CPU executes programs, performs arithmetic processing, and controls each element constituting the sending mail server 3. The auxiliary storage device stores programs executed by the CPU, registration data, etc., and may be an HDD (Hard Disk Drive) or SSD (Solid State Drive). The RAM is used as a work area for the CPU to execute programs and perform arithmetic processing.

[0052] The outgoing mail reception unit 32 receives outgoing mail sent from the sender terminal 5 under the control of the control unit 30. This outgoing mail is created by the sender terminal 5. The destination detection unit 34 detects the destination of the outgoing mail received by the outgoing mail reception unit 32 under the control of the control unit 30.

[0053] The outgoing mail sending unit 36 ​​sends outgoing mail to the destination mail server 7. This outgoing mail sending unit 36 ​​can send outgoing mail by selecting an encrypted communication path encrypted by TLS, and can also send outgoing mail through a non-encrypted communication path that is not encrypted by TLS.

[0054] The communication unit 38 transmits and receives data to and from the outside of the sending mail server 3 .

[0055] The TLS communication determination processing unit 300 includes an encrypted communication determination processing control unit 301, an outgoing mail sending setting screen providing unit 302, an outgoing mail sending setting receiving unit 303, an outgoing mail sending setting holding unit 304, an attachment detection unit 306, a TLS communication compatibility information inquiry unit 308 as an "encrypted communication compatibility information inquiry unit", a TLS communication compatibility status determination unit 310 as an "encrypted communication compatibility status determination unit", an attachment separation unit 312, a compression / decompression password generation unit 314, an attachment compression unit 316, an outgoing mail body appending unit 318, a compressed file reattachment unit 320, a password-incorporated mail creation unit 321, a sender terminal notification unit 322, an administrator terminal notification unit 324, a download URL (Uniform Resource Locator) locator generation unit 326, download password generation unit 328, attachment upload unit 330, sent mail history storage unit 332, sent mail history providing unit 334, sent mail history report creation unit 336, sent mail history report providing unit 338, pseudo screen creation unit 340, and pseudo screen providing unit 342.

[0056] The TLS communication determination processing unit 300 detects whether an attachment is attached to the outgoing mail, and if it is detected that an attachment is attached, it queries the destination mail server 7 of the outgoing mail to obtain TLS communication compatibility information as "encryption communication compatibility information" including information on whether the destination mail server 7 supports TLS. In addition to information identifying whether the destination mail server 7 supports TLS, the TLS communication compatibility information includes, for example, the TLS encryption version, the TLS server certificate, the expiration date of the TLS server certificate, and the cipher suite. If it is confirmed from the obtained TLS communication compatibility information that the destination mail server 7 supports TLS communication, the outgoing mail including the attachment is sent to the destination mail server 7 via an encrypted communication path encrypted by TLS communication. On the other hand, if it is confirmed that the destination mail server 7 does not support TLS communication, the attachment separated from the outgoing mail is sent to the attachment storage server 4 according to the attachment sending method preset in the outgoing mail sending setting holding unit 304, or the attachment is encrypted, compressed, and converted into a password-protected compressed file, and then reattached to the outgoing mail and sent to the destination mail server 7. The outgoing mail from which the attachments have been removed is sent to the destination mail server 7 via a non-encrypted communication path that is not encrypted by TLS communication.

[0057] The encrypted communication determination process control unit 301 is configured by the above-mentioned control unit 30, and controls a series of operations of the TLS communication determination process unit 300. In other words, this encrypted communication determination process control unit 301 controls the operations of each element included in the TLS communication determination process unit 300. This encrypted communication determination process control unit 301 switches the method of sending the attachment based on the TLS communication compatibility information of the destination mail server 7 acquired by the TLS communication compatibility information inquiry unit 308. This sending method includes a method of sending the attachment to the attachment storage server 4 and a method of encrypting, compressing, and converting the attachment into a password-protected compressed file and then sending it to the destination mail server 7.

[0058] The outgoing mail sending setting screen providing unit 302 provides a screen for setting the sending method of an attachment when the destination mail server 7 does not support TLS communication, and for setting the sending method of an outgoing mail with attachments removed.

[0059] 3 is a schematic diagram of an outgoing mail sending setting screen 345 for setting the sending method of an attached file when the destination mail server 7 does not support TLS communication and the sending method of an outgoing mail with an attachment removed. At the top of this outgoing mail sending setting screen 345, there is a setting section 346 for setting the sending method of an attached file, and below that there is a setting section 347 for setting the sending method of an outgoing mail with an attachment removed.

[0060] In the setting section 346 for the method of sending attachments, it is possible to select and set the method of sending attachments when the destination mail server 7 does not support TLS communication. As shown in this figure, it is possible to select and set whether to upload the attachment to the attachment storage server 4 and send it, or to compress the attachment into a password-protected compressed file and send the outgoing mail with this password-protected compressed file reattached to the destination mail server 7.

[0061] In the setting section 347 for the sending method of the outgoing mail with attachments removed, the sending method of the outgoing mail with attachments removed can be selected and set when the destination mail server 7 does not support TLS communication. As shown in this figure, from top to bottom, there are options such as "Hold for a specified time and send the outgoing mail after the specified time has elapsed", "Send the outgoing mail after adding a specified email address to the Bcc (Blind Carbon Copy) of the outgoing mail", "Cancel sending of the outgoing mail", "Send the outgoing mail after approval by a specified approver", "Send the outgoing mail and notify a preregistered email address", and "Send the outgoing mail immediately", and one of them can be selected and set.

[0062] In addition, there are provided a column for setting the hold time when "Hold the email for a specified time and send the outgoing email after the specified time has elapsed" is selected, a column for setting the email address to be added to the Bcc when "Send the outgoing email after adding the email address to the Bcc of the outgoing email", a column for setting the email address of the approver when "Send the outgoing email after the approver's approval" is selected, and a column for setting the email address to be notified when "Send the outgoing email and notify the email address to be notified" is selected.

[0063] This outgoing mail sending setting screen 345 is provided to the sender terminal 5, the administrator terminal 6, etc., and through this setting screen 345, the sending method of the attached file and the sending method of the outgoing mail with the attachment removed are set.

[0064] 2 accepts settings for the sending method of attachments when the destination mail server 7 does not support TLS communication, and settings for the sending method of outgoing mail with attachments removed, which are set on the outgoing mail sending settings screen 345. The settings accepted by this outgoing mail sending settings acceptance unit 303 are set and registered in the outgoing mail sending settings holding unit 304.

[0065] The outgoing mail sending setting storage unit 304 stores in advance the setting of the sending method of the attachment file when the destination mail server 7 does not support TLS communication, and the setting of the sending method of the outgoing mail from which the attachment file has been removed. This setting may be performed from the sender terminal 5 or the administrator terminal 6 as described above, or may be set in advance when the e-mail sending system 2 is installed.

[0066] As a method of sending an attachment when the destination mail server 7 does not support TLS communication, the attachment may be sent to the attachment storage server 4 as described above and provided by the attachment storage server 4, or the attachment may be compressed into a password-protected file and sent to the destination mail server 7.

[0067] In addition, when the destination mail server 7 does not support TLS communication, various settings can be made as the method of sending the outgoing mail with attachments removed, such as holding the outgoing mail for a specified period of time and sending the outgoing mail after the specified period has elapsed, sending the outgoing mail after adding a specified email address to the Bcc of the outgoing mail, canceling the sending of the outgoing mail, sending the outgoing mail after approval by a specified approver, sending the outgoing mail and notifying a pre-registered email address, or sending the outgoing mail immediately.

[0068] The attached file detection unit 306 detects whether or not an attachment file is attached to the outgoing mail accepted by the outgoing mail acceptance unit 32 .

[0069] The TLS communication support information inquiry unit 308 inquires of the destination mail server 7 of the outgoing mail, and acquires TLS communication support information including information on whether the destination mail server 7 supports TLS. For example, it sends an EHLO command to the destination mail server 7, and detects a response from the destination mail server 7 to that command.

[0070] The TLS communication support status determination unit 310 determines whether or not the destination mail server 7 supports TLS based on the TLS communication support information acquired by the TLS communication support information inquiry unit 308. Conditions for determining that the destination mail server 7 does not support TLS may include not only cases where TLS is not supported, but also cases where even if TLS is supported, there is a high security risk, such as a low encryption version, a certificate that cannot be traced back to the root (root certificate), an expired certificate, or a vulnerable cipher being used.

[0071] The attachment separation unit 312 separates the attachment from an outgoing mail with an attachment, and divides the outgoing mail into the attachment and the outgoing mail without the attachment.

[0072] A compression / decompression password generating unit 314 generates a compression / decompression password for compressing the separated attachment into a password-protected compressed file. This compression / decompression password also serves as the password for decompressing the password-protected compressed file.

[0073] The method of generating the compression / decompression password can be, for example, generated from a randomly generated character string, generated from a character string specified by the sender terminal 5, or using a one-time password.

[0074] When multiple attachments are attached to an outgoing email, these multiple attachments may be combined into one password-protected compressed file, or the multiple attachments may be compressed using one compression / decompression password generated by the compression / decompression password generation unit 314.

[0075] A compression / decompression password notification email separate from the outgoing email containing the compression / decompression password is created by the sending mail server 3 and sent to the destination mail server 7 .

[0076] The attachment compression unit 316 applies the compression / decompression password generated by the compression / decompression password generation unit 314 to encrypt / compress the attachment into a password-protected compressed file. As described above, when multiple attachments are attached to an outgoing email, these multiple attachments may be combined into a single compressed file.

[0077] If the destination mail server 7 supports TLS communication, the attachment can be sent to the destination mail server 7 by selecting an encrypted communication path encrypted by highly secure TLS communication, and a high level of security is also ensured for the sending path in which the attachment is sent to the attachment storage server 4 for storage, and the attachment is provided from the attachment storage server 4. Therefore, when an outgoing mail including an attachment can be sent over an encrypted communication path encrypted by TLS communication, or when an attachment is sent to the attachment storage server 4, the attachment can be sent safely without being encrypted, compressed, or converted into a password-protected compressed file. Therefore, in such cases, it is not essential to encrypt the attachment into a password-protected compressed file, and the attachment may be sent as is without being encrypted, compressed, or converted.

[0078] The outgoing mail body appending unit 318 appends text to the body of the outgoing mail based on the control of the encrypted communication determination process control unit 301. Based on the TLS communication support information of the destination mail server 7 acquired by the TLS communication support information inquiry unit 308, text indicating whether the destination mail server 7 supports TLS is appended to the body of the outgoing mail. For example, if the destination mail server 7 supports TLS, text such as "Sent via an encrypted mail communication path (TLS communication)" or "This mail was sent via an encrypted communication path encrypted by TLS communication" is appended to the body. On the other hand, if the destination mail server 7 does not support TLS, text such as "Sent via an unencrypted mail communication path (TLS communication)" or "This mail was sent via an unencrypted communication path not encrypted by TLS communication" is appended to the body.

[0079] In addition, a download URL indicating the location (address) of the attachment on the attachment storage server 4, which is generated by a download URL generation unit 326 described later, and a download password for downloading the attachment from the attachment storage server 4, which is generated by a download password generation unit 328, are also added to the body of the sent email by the sent email body appending unit 318.

[0080] FIG. 4 is a schematic diagram showing an example of a display screen of an outgoing mail including text added by the outgoing mail text adding unit 318. Such a display screen of an e-mail is displayed on the destination terminal 8. FIG. 4(a) shows a screen of an e-mail sent via a non-encrypted communication path that is not encrypted by TLS communication, and FIG. 4(b) shows a screen of an e-mail sent via an encrypted communication path that is encrypted by TLS communication. The added text 350 added by the outgoing mail text adding unit 318 is composed of an encrypted / non-encrypted transmission display 352 that displays whether the e-mail was sent via an encrypted communication path that is encrypted by TLS communication or a non-encrypted communication path that is not encrypted by TLS communication, an attachment download guide display 354 that guides downloading an attachment from the attachment storage server 4, a download URL display 356 that displays a download URL, and the like. In addition, an outgoing mail text 360 is displayed below the added text 350.

[0081] The compressed file reattachment unit 320 shown in FIG. 2 reattaches the password-protected compressed file to the outgoing mail from which the attachment was removed.

[0082] The password-containing mail creation unit 321 creates a password-containing mail (compression / decompression password notification mail) for notifying the destination terminal 8 of the compression / decompression password generated by the compression / decompression password generation unit 314. The password-containing mail contains the compression / decompression password. This password-containing mail is then sent to the destination mail server 7 as a separate mail from the outgoing mail from the sender terminal 5.

[0083] The sender terminal notification unit 322 notifies the sender terminal 5 that has sent the outgoing mail under the control of the encrypted communication determination process control unit 301. The sender terminal 5 is notified of the content indicating whether the outgoing mail has been sent to the destination mail server 7 via an encrypted communication path encrypted by TLS communication. For example, when the outgoing mail has been sent to the destination mail server 7 via an encrypted communication path encrypted by TLS communication, the sender terminal 5 is notified of the content such as "Sent via an encrypted mail communication path (TLS communication)" or "This mail has been sent via an encrypted communication path encrypted by TLS communication." On the other hand, when the outgoing mail has been sent via an unencrypted communication path that is not encrypted by TLS communication, the sender terminal 5 is notified of the content such as "Sent via an unencrypted mail communication path (TLS communication)" or "This mail has been sent via an unencrypted communication path that is not encrypted by TLS communication."

[0084] The administrator terminal notification unit 324 notifies the administrator terminal 6 of the transmission result of the outgoing mail sent from the sender terminal 5 under the control of the encrypted communication determination processing control unit 301. The administrator terminal 6 is notified of the content indicating whether the outgoing mail was sent to the destination mail server 7 via an encrypted communication path encrypted by TLS communication.

[0085] When the attachment is sent to the attachment storage server 4 for storage, the download URL generating unit 326 generates a download URL indicating the location (address) of the attachment in the attachment storage server 4.

[0086] The generated download URL is added to the body of the outgoing mail by the outgoing mail body adding unit 318.

[0087] The download password generating section 328 generates a download password for downloading an attachment stored in the attachment storage server 4.

[0088] The generated download password is added to the body of the outgoing mail by the outgoing mail body adding unit 318 .

[0089] The attachment upload unit 330 sends the attachment to the attachment storage server 4. At this time, the download URL generated by the download URL generation unit 326 and the download password generated by the download password generation unit 328 are also sent to the attachment storage server 4.

[0090] The sent mail history storage unit 332 stores the sending history information of sent mail sent from the sender terminal 5. The sending history information includes the TLS communication support information of the destination mail server 7 and the determination result of whether or not it supports TLS. The sending history information also includes information on whether or not the mail was sent to the destination mail server 7 via an encrypted communication path encrypted by TLS communication, sender information, and destination information. The sending history information is stored for each sent mail sent from the sender terminal 5.

[0091] The sent mail history providing unit 334 provides the sending history information stored in the sent mail history storage unit 332. In response to a request for sending history information sent from the sender terminal 5 or the administrator terminal 6, the requested sending history information is provided to the request source.

[0092] The sent mail history report creation unit 336 creates a sent mail history report based on the sending history information for each of the multiple sent mails stored in the sent mail history storage unit 332. This sent mail history report includes the number of encrypted communication mails, which is the number of sent mails sent to the destination mail server 7 via an encrypted communication path encrypted by TLS communication, the number of unencrypted communication mails, which is the number of sent mails sent via an unencrypted communication path not encrypted by TLS communication, and personal data that is aggregating the number of encrypted communication mails and the ratio of the number of unencrypted communication mails to the total number of sent mails for each sender and each destination, and statistical information data that is aggregating the personal data of multiple senders and multiple destinations. In addition, this sent mail history report also includes a graph display, and the number and ratio for each destination and sender in the communication via the encrypted communication path encrypted by TLS communication or the communication via the unencrypted communication path not encrypted by TLS communication are displayed in a graph format. As the graph display, for example, a heat map generation or statistical information (statistical chart) may be displayed. Here, a statistical chart refers to a graph or table used for organizing, visualizing, and analyzing multiple pieces of statistical data.

[0093] The sent mail history report providing unit 338 provides the sent mail history report created by the sent mail history report creating unit 336. In response to a request for a sent mail history report from the manager terminal 6, the sent mail history report is provided to the requesting manager terminal 6. When the manager terminal 6 receives the sent mail history report, the sent mail history report including, for example, heat map generation and statistical information (statistical charts) is displayed on the screen of the manager terminal 6.

[0094] Pseudo screen creation unit 340 creates a pseudo display screen on which text has been added to the text of an outgoing mail by outgoing mail text appending unit 318. This pseudo screen creation unit 340 creates a pseudo screen that is configured with a pseudo representation of the text of the mail text after appending by outgoing mail text appending unit 318, assuming that the outgoing mail from sender terminal 5 has been sent over an encrypted communication path encrypted by TLS communication, or assuming that the outgoing mail has been sent over an unencrypted communication path not encrypted by TLS communication. This pseudo screen creation unit 340 can create a pseudo screen regardless of whether an outgoing mail is sent or not.

[0095] In addition, this pseudo screen creation unit 340 creates a pseudo screen by simulating the text of the email body to which the download URL and download password have been added by the outgoing email body addition unit 318, assuming that the attachment has been sent to the attachment storage server 4.

[0096] The pseudo screen providing unit 342 provides a pseudo screen of the outgoing mail created by the pseudo screen creating unit 340. In response to a request for providing a pseudo screen from the administrator terminal 6, the pseudo screen is provided to the administrator terminal 6 which is the request source. Then, when the administrator terminal 6 receives the pseudo screen, the pseudo screen is displayed on the screen of the administrator terminal 6. In this way, the pseudo screen can be checked in advance without sending the outgoing mail.

[0097] The above is an explanation of the functional block diagram of the sending mail server 3.

[0098] In this sending mail server 3, when the attachment detection unit 306 detects that an attachment is attached to the sending mail, the encrypted communication determination process control unit 301 causes the TLS communication compatibility information inquiry unit 308 to acquire TLS communication compatibility information of the destination mail server 7, and when it is confirmed from the acquired TLS communication compatibility information that the destination mail server 7 supports TLS, causes the sending mail sending unit 36 ​​to select an encrypted communication path encrypted by TLS and send the sending mail including the attachment to the destination mail server 7. On the other hand, when it is confirmed that the destination mail server 7 does not support TLS, causes the attachment upload unit 330 to send the attachment separated from the sending mail to the attachment storage server 4, and causes the sending mail sending unit 36 ​​to send the sending mail from which the attachment has been removed to the destination mail server 7 through a non-encrypted communication path not encrypted by TLS. Alternatively, the attachment separated from the sending mail is compressed into a password-protected compressed file, and causes the sending mail to which the password-protected compressed file has been reattached to be sent from the sending mail sending unit 36 ​​to the destination mail server 7 through a non-encrypted communication path not encrypted by TLS.

[0099] 5 is a schematic functional block diagram of the attachment file storage server 4 included in the email transmission system 2. This attachment file storage server 4 stores attachment files and provides the stored attachment files in response to a request for providing the attachment files.

[0100] The attachment storage server 4 is configured to include an attachment storage server control unit 40, an attachment reception unit 41, an attachment storage unit 42, a download URL reception unit 43, a download password reception unit 44, an attachment provision request reception unit 45, a download password confirmation unit 46, an attachment provision unit 47, and a communication unit 48.

[0101] The attachment storage server control unit 40 is configured to include a CPU, an auxiliary storage device which is a non-volatile storage device, and a RAM (not shown). The CPU executes programs and performs arithmetic processing, and the attachment storage server control unit 40 controls each element constituting the attachment storage server 4.

[0102] The attachment reception unit 41 receives attachments sent from the sending mail server 3 under the control of the attachment storage server control unit 40 .

[0103] The attached file storage unit 42 stores the attached file accepted by the attached file accepting unit 41 .

[0104] The download URL acceptance unit 43 accepts and stores the download URL sent from the sending mail server 3.

[0105] The attached files stored in the attachment storage unit 42 are associated with the download URLs accepted by the download URL acceptance unit 43, and the association information between the attached files and the download URLs is stored in the attachment storage unit 42. When this download URL is accessed from an external destination terminal 8 or the like that is the source of the attachment request, the attached file associated with this download URL is downloaded.

[0106] The download password reception unit 44 receives and stores the download password sent from the sending mail server 3. This download password is a password that is required to be entered when downloading an attachment, and if it matches the entered password, downloading is permitted.

[0107] The attachment request receiving unit 45 receives a request for providing an attachment file from an external device such as the destination terminal 8. This request is generated by accessing a download URL from an external device that is the source of the request.

[0108] A download password confirmation section 46 receives an input download password sent from a request source for providing the attachment file, compares the received input password with the download password received by a download password reception section 44, and permits downloading of the attachment file if they match, and prohibits downloading if they do not match.

[0109] The attachment providing unit 47 provides the attachment by downloading it to the request source that sent the request.

[0110] The communication unit 48 transmits and receives data to and from the outside.

[0111] When the sending mail server 3 confirms that the destination mail server 7 does not support TLS, the encrypted communication determination processing control unit 301 of the sending mail server 3 sends the attachment separated from the outgoing email from the attachment upload unit 330 to the attachment storage server 4.

[0112] In the attachment storage server 4, the attachment received from the sending mail server 3 is received by the attachment receiving unit 41, and the received attachment is stored in the attachment storage unit 42. After the attachment is stored in the attachment storage unit 42 in this way, for example, when the destination terminal 8 or the like accesses the download URL and sends a request for the attachment, this request is received by the attachment request receiving unit 45. Next, when an input download password is sent from the destination terminal 8 or the like which is the source of the request, the download password confirmation unit 46 receives it and judges whether it matches the correct download password. If it matches, downloading of the attachment is permitted, and the attachment is provided from the attachment providing unit 47 to the destination terminal 8 or the like which is the source of the request.

[0113] Next, the operation of the electronic mail system 1 including the electronic mail transmission system 2 according to the first embodiment of the present invention will be described.

[0114] Fig. 6 is a schematic diagram showing the flow of sending an e-mail in this e-mail system 1. However, it is a diagram showing the flow of sending an attachment to the attachment storage server 4 when the destination mail server 7 does not support TLS. It is also a diagram showing the setting flow for immediately sending an outgoing e-mail with attachments removed when the destination mail server 7 does not support TLS.

[0115] First, a mail to be sent is created using the sender terminal 5 (step S100), and the created mail to be sent is sent to the sending mail server 3 (step S101).

[0116] The sending mail server 3 receives an outgoing mail sent from the sender terminal 5 (step S200), and checks whether or not an attachment file is attached to the received outgoing mail (step S201).

[0117] If no attachment is included (No in step S201), the accepted outgoing mail is sent to the destination mail server 7 (step S230).

[0118] On the other hand, if an attachment is included (Yes in step S201), the sending mail server 3 inquires of the destination mail server 7 as to whether or not it supports TLS (step S202). When the destination mail server 7 receives this inquiry (step S400), it sends TLS communication compatibility information to the sending mail server 3 (step S401).

[0119] When the sending mail server 3 acquires the TLS communication support information (step S203), it determines whether or not the destination mail server 7 supports TLS based on the acquired TLS communication support information (step S204).

[0120] If the destination mail server 7 supports TLS (Yes in step S204), a note is added to the body of the outgoing mail indicating that the outgoing mail will be sent via an encrypted communication path encrypted by TLS (step S220). Then, the outgoing mail including the attachment is sent to the destination mail server 7 via the encrypted communication path encrypted by TLS (step S221). Then, the sender terminal 5 is notified that the outgoing mail including the attachment has been sent via the encrypted communication path encrypted by TLS (step S222).

[0121] On the other hand, if the destination mail server 7 does not support TLS (No in step S204), a note is added to the body of the outgoing mail indicating that the outgoing mail will be sent via a non-encrypted communication path that is not encrypted by TLS communication (step S205). After that, the attachment is separated from the outgoing mail (step S206), and the separated attachment is sent to the attachment storage server 4 (step S207). The attachment storage server 4 accepts the sent attachment (step S300) and stores it (step S301).

[0122] Next, the sender mail server 3 sends the outgoing mail from which the attachment has been removed to the destination mail server 7 through a non-encrypted communication path that has not been encrypted by TLS (step S208). After that, the sender terminal 5 is notified that the outgoing mail from which the attachment has been removed has been sent without encryption (step S209).

[0123] When the destination mail server 7 receives the outgoing mail from the sender mail server 3 with the attachment removed, it stores the outgoing mail (step S402). When the destination terminal 8, which is the destination of the outgoing mail, requests the destination mail server 7 to view the outgoing mail, the destination mail server 7 sends the stored outgoing mail addressed to the destination terminal 8 to the destination terminal 8 (step S403).

[0124] The destination terminal 8 receives the outgoing mail sent from the destination mail server 7 (step S500) and displays it on the screen. When the destination terminal 8 makes a request for providing the attached file stored in the attachment file storage server 4 (step S501), the attachment file storage server 4 that receives this request (step S302) provides the attached file in response to the request (step S303). The destination terminal 8 that made the request for the attachment accepts the attached file (step S502) and views it.

[0125] In addition, when sending an outgoing mail without an attachment (No in step S201) (step S230), the sending mail server 3 inquires of the destination mail server 7 whether it supports TLS. If the destination mail server 7 supports TLS, a note is added to the body of the outgoing mail indicating that the outgoing mail will be sent via an encrypted communication path encrypted by TLS. Then, the outgoing mail is sent to the destination mail server 7 via the encrypted communication path encrypted by TLS. Then, the sender terminal 5 is notified that the outgoing mail has been sent via an encrypted communication path encrypted by TLS. On the other hand, if the destination mail server 7 does not support TLS, a note is added to the body of the outgoing mail indicating that the outgoing mail will be sent via a non-encrypted communication path that is not encrypted by TLS. Then, the outgoing mail is sent to the destination mail server 7 via a non-encrypted communication path that is not encrypted by TLS. Then, the sender terminal 5 is notified that the outgoing mail has been sent without encryption.

[0126] 7 is a schematic diagram showing the flow of sending an e-mail in this e-mail system 1. However, if the destination mail server 7 does not support TLS, the diagram shows the flow of compressing the attached file into a password-protected compressed file, reattaching the compressed file to the outgoing e-mail, and sending it to the destination mail server 7. The diagram also shows the setting flow of immediately sending an outgoing e-mail with a password-protected compressed file attached if the destination mail server 7 does not support TLS.

[0127] First, a mail to be sent is created using the sender terminal 5 (step S150), and the created mail to be sent is sent to the sending mail server 3 (step S151).

[0128] The sending mail server 3 receives an outgoing mail sent from the sender terminal 5 (step S250), and checks whether or not an attachment file is attached to the received outgoing mail (step S251).

[0129] If no attachment is included (No in step S251), the accepted outgoing mail is sent to the destination mail server 7 (step S280).

[0130] On the other hand, if an attachment is included (Yes in step S251), the sending mail server 3 inquires of the destination mail server 7 as to whether or not it supports TLS (step S252). When the destination mail server 7 receives this inquiry (step S450), it sends TLS communication compatibility information to the sending mail server 3 (step S451).

[0131] When the sending mail server 3 acquires the TLS communication support information (step S253), it determines whether or not the destination mail server 7 supports TLS based on the acquired TLS communication support information (step S254).

[0132] If the destination mail server 7 supports TLS (Yes in step S254), a note is added to the body of the outgoing mail indicating that the outgoing mail will be sent via an encrypted communication path encrypted by TLS (step S270). Then, the outgoing mail including the attachment is sent to the destination mail server 7 via the encrypted communication path encrypted by TLS (step S271). Then, the sender terminal 5 is notified that the outgoing mail including the attachment has been sent via the encrypted communication path encrypted by TLS (step S272).

[0133] On the other hand, if the destination mail server 7 does not support TLS (No in step S254), a note is added to the body of the outgoing mail indicating that the outgoing mail will be sent via a non-encrypted communication path that is not encrypted by TLS communication (step S255). After that, the attachment is separated from the outgoing mail (step S256), and the compression / decompression password generating unit 314 generates a compression / decompression password (step S257). Next, the generated compression / decompression password is applied to encrypt and compress the attachment to generate a password-protected compressed file (step S258). This password-protected compressed file is reattached to the outgoing mail (step S259), and the outgoing mail with the compressed file attached is sent to the destination mail server 7 via a non-encrypted communication path that is not encrypted by TLS (step S260). Then, the mail containing the compression / decompression password is sent from the sending mail server 3 to the destination mail server 7 (step S261). Thereafter, the sender terminal 5 is notified that the outgoing mail to which the password-protected compressed file is attached has been sent via a non-encrypted communication path that has not been encrypted by TLS communication (step S262).

[0134] When the destination mail server 7 receives the outgoing mail with the password-protected compressed file attached and the mail containing the compression / decompression password from the sender mail server 3, it stores the outgoing mail (step S452). When the destination terminal 8, which is the destination of the outgoing mail, requests the destination mail server 7 to view the outgoing mail, the destination mail server 7 sends the stored outgoing mail addressed to the destination terminal 8 to the destination terminal 8 (step S453).

[0135] The destination terminal 8 receives the outgoing mail with the password-protected compressed file attached and the mail with the compression / decompression password sent from the destination mail server 7 (step S550). Then, the password-protected compressed file is decompressed by applying the compression / decompression password, and the decompressed file is decrypted and decompressed to the original attachment (step S551). This decompression process allows the destination terminal 8 to view the decompressed attachment.

[0136] In addition, when sending an outgoing mail without an attachment (No in step S251) (step S280), the sending mail server 3 inquires of the destination mail server 7 whether it supports TLS. If the destination mail server 7 supports TLS, a note is added to the body of the outgoing mail indicating that the outgoing mail will be sent via an encrypted communication path encrypted by TLS. Then, the outgoing mail is sent to the destination mail server 7 via the encrypted communication path encrypted by TLS. Then, the sender terminal 5 is notified that the outgoing mail has been sent via an encrypted communication path encrypted by TLS. On the other hand, if the destination mail server 7 does not support TLS, a note is added to the body of the outgoing mail indicating that the outgoing mail will be sent via a non-encrypted communication path that is not encrypted by TLS. Then, the outgoing mail is sent to the destination mail server 7 via a non-encrypted communication path that is not encrypted by TLS. Then, the sender terminal 5 is notified that the outgoing mail has been sent without encryption.

[0137] Next, the effects of the first embodiment of the present invention will be described.

[0138] According to the first embodiment, when it is confirmed that the destination mail server 7 supports TLS, an encrypted communication path encrypted by TLS is selected and the outgoing mail including the attachment is sent to the destination mail server 7, whereas when it is confirmed that the destination mail server 7 does not support TLS, the attachment is sent based on the setting of the outgoing mail sending setting storage unit 304 and the outgoing mail with the attachment removed is sent to the destination mail server 7 through a non-encrypted communication path not encrypted by TLS. This makes it possible to realize an e-mail sending system which safely sends attachments and does not cause e-mail interruptions.

[0139] Also, according to the first embodiment, when the destination mail server 7 does not support TLS, the attachment can be sent by either sending the attachment to the attachment storage server 4 and providing the attachment via the attachment storage server 4, or compressing the attachment into a password-protected compressed file, attaching the password-protected compressed file to an outgoing mail, and sending it to the destination mail server 7. This allows the attachment to be sent safely. A higher level of safety is ensured by the sending method using the attachment storage server 4. On the other hand, the method of attaching a password-protected compressed file to an outgoing mail and sending it to the destination mail server 7 does not require the attachment storage server 4 to be installed, and the system configuration can be simplified.

[0140] Furthermore, according to the first embodiment, when the destination mail server 7 does not support TLS, the method of sending the attachment can be selected from either sending the attachment to the attachment storage server 4 and providing the attachment via the attachment storage server 4, or compressing the attachment into a password-protected compressed file, attaching the password-protected compressed file to an outgoing mail, and sending it to the destination mail server 7. This makes it easy to set the method of sending the attachment, and realizes a system that is easy to introduce and easy to use.

[0141] Furthermore, according to the first embodiment, there are multiple methods for sending outgoing mail with attachments removed when the destination mail server 7 does not support TLS, and various settings are possible. Also, settings can be flexibly realized according to the needs of the user.

[0142] Furthermore, according to the first embodiment, the sending method for outgoing mails with attachments removed when the mail does not support TLS can be selected from among multiple options. This makes it easy to set the sending method, and realizes a system that is easy to introduce and easy to use.

[0143] Furthermore, according to this embodiment 1, a sentence indicating whether or not the destination mail server 7 supports TLS is added to the body of the outgoing mail, so that when you receive an outgoing mail, you can check whether or not the mail was sent through an encrypted communication path encrypted by TLS.

[0144] Furthermore, according to the first embodiment, it is possible for the sender terminal 5 of the outgoing mail to check whether the outgoing mail has been sent through an encrypted communication path encrypted by TLS.

[0145] Furthermore, according to the first embodiment, the administrator terminal 6 can check whether or not an outgoing mail has been sent through an encrypted communication path encrypted by TLS.

[0146] In addition, according to this embodiment 1, by checking the created sent email history report, it is possible to perform a detailed analysis of the history, such as how many sent emails were sent through an encrypted communication path encrypted by TLS.

[0147] Furthermore, according to the first embodiment, it is possible to check in advance the display screen of the outgoing mail that will be delivered to the destination.

[0148] [Embodiment 2 of the invention] In the above-described first embodiment of the present invention, when it is detected that an attachment is attached to an outgoing mail, it is configured to determine whether or not the destination mail server 7 supports TLS communication.

[0149] In the second embodiment of the present invention, whether or not the destination mail server 7 supports TLS communication is determined when sending an outgoing mail, regardless of whether or not there is an attachment. An e-mail transmission system 2A according to the second embodiment of the present invention will be described below, where elements that are the same as or similar to the e-mail system 1 and the e-mail transmission system 2 according to the first embodiment described above are given the same reference numerals and duplicated descriptions will be omitted.

[0150] A second embodiment of the present invention will be described with reference to FIGS.

[0151] FIG. 8 is a configuration block diagram that shows in outline an electronic mail system 1A including an electronic mail transmission system 2A according to the second embodiment of the present invention.

[0152] This configuration is the same as that of the email system 1 according to the first embodiment of the present invention (see FIG. 1), except that the attachment file storage server 4 is removed.

[0153] This electronic mail transmission system 2A includes a sending mail server 3A that sends out an outgoing mail created on a sender terminal 5 to a destination mail server 7.

[0154] 9 is a schematic functional block diagram of the sending mail server 3 A. Elements related to the attachment storage server 4, such as the download URL generating unit 326, the download password generating unit 328, and the attachment uploading unit 330, are removed from the configuration of the sending mail server 3 according to the first embodiment of the present invention (see FIG. 2).

[0155] Before the sending mail server 3 sends an outgoing mail to the destination mail server 7, the sending mail server 3 determines whether the destination mail server 7 supports TLS. If the destination mail server 7 supports TLS, the sending mail server 3 selects an encrypted communication path encrypted by TLS communication and sends the outgoing mail. On the other hand, if the destination mail server 7 does not support TLS, the sending mail server 3 sends the outgoing mail based on the sending method for outgoing mail preset in the outgoing mail sending setting storage unit 304.

[0156] The outgoing mail sending setting screen providing section 302 provides a screen for setting the sending method of outgoing mail when the destination mail server 7 does not support TLS communication. Specifically, the same setting selection items as those in the setting section 347 for the sending method of outgoing mail excluding attachments in the outgoing mail sending setting screen 345 shown in Fig. 3 are displayed on the screen as the sending method of outgoing mail. By performing an input operation on this screen, the sending method of outgoing mail when the destination mail server 7 does not support TLS communication can be selected and set.

[0157] The methods for sending outgoing mail include "Hold the outgoing mail for a specified period of time and send it after the specified period has elapsed", "Send the outgoing mail after adding a specified email address to the Bcc field of the outgoing mail", "Cancel sending of the outgoing mail", "Send the outgoing mail after approval by a specified approver", "Send the outgoing mail and notify a pre-registered email address", and "Send the outgoing mail immediately", and you can select one of them to set.

[0158] This outgoing mail sending setting screen is provided to the sender terminal 5, the administrator terminal 6, etc., and the sending method of the outgoing mail is set through this setting screen.

[0159] The outgoing mail sending setting reception unit 303 receives the setting of the sending method of the outgoing mail when the destination mail server 7 does not support TLS communication, which is set on the outgoing mail sending setting screen. The setting received by this outgoing mail sending setting reception unit 303 is set and registered in the outgoing mail sending setting holding unit 304.

[0160] In addition, if an outgoing mail has an attachment, and if the destination mail server 7 supports TLS, the outgoing mail including the attachment is sent to the destination mail server 7 via an encrypted communication path encrypted based on TLS. On the other hand, if the destination mail server 7 does not support TLS, the attachment is encrypted and compressed into a password-protected compressed file, and this password-protected compressed file is reattached to the outgoing mail and sent to the destination mail server 7 via an unencrypted communication path that is not encrypted by TLS. Next, an email containing the compression / decompression password to the same destination is sent to the destination mail server 7.

[0161] If the destination mail server 7 supports TLS, the attachment is sent safely via an encrypted communication path encrypted by TLS, and if the destination mail server 7 does not support TLS, the attachment is encrypted, compressed, and converted into a password-protected compressed file before being sent, so that the attachment can be sent safely.

[0162] The sending mail server 3A includes an outgoing mail reception unit 32 that receives the created outgoing mail from the sender terminal 5, a TLS communication compatibility information inquiry unit 308 that acquires TLS communication compatibility information from the destination mail server 7 of the outgoing mail including information on whether the destination mail server 7 of the outgoing mail supports TLS, an outgoing mail sending setting storage unit 304 that stores in advance settings for the sending method of the outgoing mail when the destination mail server 7 does not support TLS, an outgoing mail sending unit 36 ​​that sends the outgoing mail to the destination mail server 7, and an encrypted communication determination processing control unit 301 that controls the sending operation of the outgoing mail based on the TLS communication compatibility information acquired by the TLS communication compatibility information inquiry unit 308.

[0163] This encrypted communication determination processing control unit 301 causes the TLS communication compatibility information inquiry unit 308 to acquire TLS communication compatibility information of the destination mail server 7, and when it is confirmed from the acquired TLS communication compatibility information that the destination mail server 7 supports TLS, it selects an encrypted communication path encrypted by TLS and causes the outgoing mail sending unit 36 ​​to send the outgoing mail to the destination mail server 7. On the other hand, when it is confirmed that the destination mail server 7 does not support TLS, it causes the outgoing mail sending unit 36 ​​to send the outgoing mail through a non-encrypted communication path not encrypted by TLS based on the settings of the outgoing mail sending setting holding unit 304.

[0164] The method of sending an outgoing mail set in the outgoing mail sending setting storage unit 304 can be selected from among the following: to hold the outgoing mail for a specified period of time and then send the outgoing mail after the specified period of time has elapsed; to send the outgoing mail after adding a specified email address to the Bcc field of the outgoing mail; to cancel sending the outgoing mail; to send the outgoing mail after approval by a specified approver; to send the outgoing mail and notify a pre-registered email address; or to send the outgoing mail immediately.

[0165] Next, the operation of the electronic mail system 1A including the electronic mail transmission system 2A according to the second embodiment of the present invention will be described.

[0166] FIG. 10 is a schematic diagram showing the flow of sending an e-mail in this e-mail system 1A.

[0167] First, a mail to be sent is created using the sender terminal 5 (step S600), and the created mail to be sent is sent to the sending mail server 3A (step S601).

[0168] When the sending mail server 3A receives an outgoing mail sent from the sender terminal 5 (step S700), it inquires of the destination mail server 7 as to whether or not it supports TLS (step S701). When the destination mail server 7 receives this inquiry (step S800), it sends TLS communication compatibility information to the sending mail server 3A (step S801).

[0169] When the sending mail server 3 acquires TLS communication support information (step S702), it determines whether or not the destination mail server 7 supports TLS based on the acquired TLS communication support information (step S703).

[0170] If the destination mail server 7 supports TLS (Yes in step S703), a note is added to the body of the outgoing mail indicating that the outgoing mail will be sent via an encrypted communication path encrypted by TLS (step S710). The outgoing mail is then sent to the destination mail server 7 via the encrypted communication path encrypted by TLS (step S711). The sender terminal 5 is then notified that the outgoing mail has been sent via an encrypted communication path encrypted by TLS (step S712).

[0171] On the other hand, if the destination mail server 7 does not support TLS (No in step S703), a note is added to the body of the outgoing mail indicating that the outgoing mail will be sent via a non-encrypted communication path that is not encrypted by TLS communication (step S704). After that, the outgoing mail is sent to the destination mail server 7 by the outgoing mail sending method set in the outgoing mail sending setting storage unit 304 (step S705). However, depending on the setting of the outgoing mail sending setting storage unit 304, the sending of the outgoing mail may be stopped. The outgoing mail sending method set in the outgoing mail sending setting storage unit 304 is any one of (1) holding the outgoing mail for a predetermined time and sending the outgoing mail after the predetermined time has elapsed, (2) adding a predetermined e-mail address to the Bcc of the outgoing mail and then sending the outgoing mail, (3) stopping the sending of the outgoing mail, (4) sending the outgoing mail after approval by a predetermined approver, (5) sending the outgoing mail and notifying a previously registered e-mail address, and (6) sending the outgoing mail immediately.

[0172] Thereafter, the sender terminal 5 is notified that the outgoing mail has been sent via a non-encrypted communication path that has not been encrypted by TLS communication (step S706).

[0173] When the destination mail server 7 receives an outgoing mail from the sender mail server 3A, it stores the outgoing mail (step S802). When the destination terminal 8, which is the destination of the outgoing mail, requests the destination mail server 7 to view the outgoing mail, the destination mail server 7 sends the stored outgoing mail addressed to the destination terminal 8 to the destination terminal 8 (step S803).

[0174] The destination terminal 8 receives the sent mail (step S900).

[0175] Next, the effects of the second embodiment of the present invention will be described.

[0176] According to the second embodiment, when it is confirmed that the destination mail server 7 supports TLS, the outgoing mail is sent to the destination mail server 7 by selecting an encrypted communication path encrypted by TLS, and on the other hand, when it is confirmed that the destination mail server 7 does not support TLS, the outgoing mail is sent to the destination mail server 7 through a non-encrypted communication path that is not encrypted by TLS based on the setting of the outgoing mail sending setting storage unit 304. As a result, when the destination mail server 7 supports TLS, the outgoing mail is sent safely by TLS communication, and when the destination mail server 7 does not support TLS, the outgoing mail is sent by a sending method that is set in advance. Therefore, the sender or administrator of the outgoing mail can know in advance the safety when the destination mail server 7 does not support TLS communication. In addition, an e-mail sending system in which e-mails are not interrupted can be realized.

[0177] According to the second embodiment, there are multiple methods for sending outgoing mail when the destination mail server 7 does not support TLS, and various settings are possible. Also, settings can be flexibly realized according to the needs of users such as senders and administrators of outgoing mail.

[0178] Furthermore, according to the second embodiment, the sending method of the outgoing mail when the destination mail server 7 does not support TLS can be selected from multiple options. This allows the sending method to be easily set, realizing a system that is easy to introduce and easy to use. [Explanation of symbols]

[0179] 1, 1A... electronic mail system, 2, 2A... electronic mail transmission system, 3, 3A... sending mail server, 4... attachment storage server, 5... sender terminal, 6... administrator terminal, 7... destination mail server, 8... destination terminal, 9... communication line, 30... control unit, 32... sending mail reception unit, 34... destination detection unit, 36... sending mail sending unit, 38... communication unit, 300, 300A... TLS communication determination processing unit (encrypted communication determination processing unit), 301... encrypted communication determination processing control unit, 3 02...Outgoing mail sending setting screen providing unit, 303...Outgoing mail sending setting receiving unit, 304...Outgoing mail sending setting holding unit, 306...Attachment detection unit, 308...TLS communication support information inquiry unit (encrypted communication support information inquiry unit), 310...TLS communication support status determination unit (encrypted communication support status determination unit), 312...Attachment separation unit, 314...Compression / decompression password generation unit, 316...Attachment compression unit, 318...Outgoing mail body appending unit, 320...Compressed file replay unit Attachment section, 321... password-inclusive email creation section, 322... sender terminal notification section, 324... administrator terminal notification section, 326... download URL generation section, 328... download password generation section, 330... attachment upload section, 332... sent email history storage section, 334... sent email history providing section, 336... sent email history report creation section, 338... sent email history report providing section, 340... pseudo screen creation section, 342... pseudo screen providing section, 350... additional text, 352... encrypted / unencrypted transmission display, 354... attachment download guide display, 356... download URL display, 360... email body, 40... attachment storage server control section, 41... attachment reception section, 42... attachment storage section, 43... download URL reception section, 44... download password reception section, 45... attachment provision request reception section, 46... download password confirmation section, 47... attachment provision section, 48... communication section

Claims

1. An electronic mail transmission system including a sender mail server that sends an outgoing mail created by a sender terminal to a destination mail server, The sending mail server: an outgoing mail reception unit that receives the created outgoing mail from the sender terminal; an attachment detection unit that detects whether or not an attachment is attached to the received outgoing mail; an encrypted communication support information inquiry unit that acquires encrypted communication support information including information on whether the destination mail server of the outgoing mail supports encrypted communication from the destination mail server; an attachment separation unit that separates the attachment from the outgoing mail and divides the outgoing mail into the attachment and the outgoing mail from which the attachment has been removed; a sending mail sending setting storage unit that stores in advance a setting for a sending method of the attachment when the destination mail server does not support encrypted communication; an outgoing mail sending unit for sending the outgoing mail to the destination mail server; an encrypted communication determination process control unit that controls a sending operation of the outgoing mail based on the encrypted communication compatibility information acquired by the encrypted communication compatibility information inquiry unit; The encrypted communication determination process control unit: When the attachment detection unit detects that the outgoing mail has an attachment, the encrypted communication compatibility information inquiry unit is caused to acquire the encrypted communication compatibility information of the destination mail server; When it is confirmed from the acquired encrypted communication compatibility information that the destination mail server is compatible with the encrypted communication, an encrypted communication path encrypted by the encrypted communication is selected and the outgoing mail including the attachment is sent to the outgoing mail sending unit toward the destination mail server, When it is confirmed that the destination mail server does not support the encrypted communication, the attachment separated from the outgoing mail by the attachment separation unit is sent based on the settings of the outgoing mail sending setting storage unit, and the outgoing mail from which the attachment has been removed is sent to the outgoing mail sending unit toward the destination mail server through a non-encrypted communication path that is not encrypted by the encrypted communication.

2. an attachment storage server that stores the attachment and provides the stored attachment in response to a request for providing the attachment; The attachment storage server includes: an attachment reception unit that receives the attachment sent from the sending mail server; an attachment storage unit that stores the received attachment; an attachment request receiving unit that receives a request for providing the attachment stored in the attachment storage unit; an attachment providing unit for providing the attachment to a request source that has sent the provision request; The sending mail server: an attachment upload unit that transmits the attachment to the attachment storage server; Furthermore, the sending mail server a compression / decompression password generating unit that generates a compression / decompression password that is applied to an encryption / compression conversion for compressing the attached file into a password-protected compressed file and is also applied to a decryption / decompression conversion for decompressing the password-protected compressed file into the attached file before compression; an attachment compression unit that applies the generated compression / decompression password to encrypt, compress, and convert the attachment into the password-protected compressed file; a compressed file reattachment unit that reattaches the password-protected compressed file created by the attachment compression unit to the outgoing email from which the attachment has been removed, The attachment storage server includes: the attachment receiving unit receives the attachment sent from the attachment upload unit, and the received attachment is stored in the attachment storage unit. When the attachment provision request receiving unit receives the provision request for the attachment, the attachment providing unit provides the attachment to the request source that sent the provision request, The sending mail server: the attachment compression unit applies the compression / decompression password generated by the compression / decompression password generation unit to the attachment separated by the attachment separation unit to create the password-protected compressed file, the compressed file re-attachment unit re-attaches the created password-protected compressed file to the outgoing mail from which the attachment has been removed, and then transmits the outgoing mail with the password-protected compressed file attached from the outgoing mail transmission unit to the destination mail server via the unencrypted communication path, The sending method of the attachment set in the sending mail sending setting storage unit is: The email sending system according to claim 1, characterized in that the system is configured to selectively send the attachment separated by the attachment separation unit from the attachment upload unit to the attachment storage server, or compress the attachment separated by the attachment separation unit into the password-protected compressed file and send the outgoing email with the password-protected compressed file attached from the outgoing email sending unit to the destination mail server.

3. A method for sending the outgoing mail from which the attachment has been removed is also preset in the outgoing mail sending setting storage unit, The encrypted communication determination process control unit When it is confirmed that the destination mail server does not support the encrypted communication, the outgoing mail from which the attachment has been removed by the attachment separation unit is sent from the outgoing mail sending unit based on the setting of the outgoing mail sending setting holding unit, The method of sending the outgoing mail from which the attachment has been removed, which is set in the outgoing mail sending setting storage unit, is holding the mail for a predetermined period of time and sending the mail after the predetermined period of time has elapsed; adding a predetermined email address to a blind carbon copy of the outgoing email and then sending the outgoing email; Stop sending the outgoing email; sending the transmission email after approval by a predetermined approver; Send the outgoing email and notify a pre-registered email address. Or, Immediately send the outgoing mail; 3. The electronic mail transmission system according to claim 2, wherein the electronic mail transmission system is set so as to be selectable between the above two options.

4. The sending mail server: a sending mail body appending unit that appends text to the body of the sending mail; The encrypted communication determination process control unit The electronic mail sending system according to claim 2 or 3, characterized in that the sending mail body appending unit is controlled so as to append a sentence indicating whether the destination mail server supports the encrypted communication to the body of the sending mail based on the encrypted communication support information of the destination mail server acquired by the encrypted communication support information inquiry unit.

5. The sending mail server: a sender terminal notification unit for notifying the sender terminal that has sent the outgoing mail; The encrypted communication determination process control unit The electronic mail sending system according to claim 4, characterized in that the sender terminal notification unit is controlled so as to notify the sender terminal of information indicating whether the outgoing mail has been sent to the destination mail server through the encrypted communication path.

6. an administrator terminal for managing the e-mail sending state of the sender terminal is communicably connected to the sending mail server; The sending mail server: a manager terminal notifying unit for notifying the manager terminal of a transmission result of the outgoing mail sent from the sender terminal; The encrypted communication determination process control unit The electronic mail sending system according to claim 5, characterized in that the administrator terminal notification unit is controlled so as to notify the administrator terminal notification unit of information indicating whether the outgoing email has been sent to the destination mail server through the encrypted communication path.

7. The sending mail server: a sent mail history storage unit for storing, for each sent mail sent from the sender terminal, sending history information including information on whether the sent mail has been sent to the destination mail server through the encrypted communication path, sender information, and destination information; a sent mail history report creating unit that creates a sent mail history report based on the sending history information of the plurality of sent mails stored in the sent mail history storage unit; a sending mail history report providing unit that provides the sending mail history report created by the sending mail history report creating unit, The sent email history report includes: The email sending system according to claim 6, characterized in that it includes personal data compiled by sender and / or recipient, which is the number of encrypted communication emails, which is the number of outgoing emails sent to the destination mail server through the encrypted communication path, the number of unencrypted communication emails, which is the number of outgoing emails sent through the unencrypted communication path, and the ratio of the number of encrypted communication emails or the number of unencrypted communication emails to the total number of outgoing emails, or statistical information data compiled by the personal data of multiple senders and / or multiple recipients.

8. The sending mail server: a pseudo screen creation unit that creates a pseudo display screen on which the sending mail body appending unit adds text to the sending mail body; a pseudo screen providing unit that provides a pseudo screen of the transmission mail created by the pseudo screen creating unit, An email sending system as described in claim 4, characterized in that the pseudo screen of the sent email can be created when the destination mail server supports the encrypted communication and the sent email is sent through the encrypted communication path, and the pseudo screen of the sent email can be created when the destination mail server does not support the encrypted communication and the sent email is sent through the unencrypted communication path, regardless of the sending of the sent email.

9. An electronic mail transmission system including a sender mail server that sends an outgoing mail created by a sender terminal to a destination mail server, The sending mail server: an outgoing mail reception unit that receives the created outgoing mail from the sender terminal; an encrypted communication support information inquiry unit that acquires encrypted communication support information including information on whether the destination mail server of the outgoing mail supports encrypted communication from the destination mail server; an outgoing mail sending setting storage unit that stores in advance a setting for a method of sending the outgoing mail when the destination mail server does not support encrypted communication; an outgoing mail sending unit for sending the outgoing mail to the destination mail server; an encrypted communication determination process control unit that controls a sending operation of the outgoing mail based on the encrypted communication compatibility information acquired by the encrypted communication compatibility information inquiry unit; The encrypted communication determination process control unit: causing the encrypted communication support information inquiry unit to obtain the encrypted communication support information of the destination mail server; When it is confirmed from the acquired encrypted communication compatibility information that the destination mail server is compatible with the encrypted communication, an encrypted communication path encrypted by the encrypted communication is selected and the outgoing mail is sent to the outgoing mail sending unit toward the destination mail server, An electronic mail sending system characterized in that, when it is confirmed that the destination mail server does not support the encrypted communication, the sending mail is sent to the sending mail sending unit through a non-encrypted communication path that is not encrypted by the encrypted communication, based on the settings of the sending mail sending setting storage unit.

10. The sending method of the outgoing mail set in the outgoing mail sending setting storage unit is holding the mail for a predetermined period of time and sending the mail after the predetermined period of time has elapsed; adding a predetermined email address to a blind carbon copy of the outgoing email and then sending the outgoing email; Stop sending the outgoing mail; sending the transmission email after approval by a predetermined approver; Send the outgoing email and notify a pre-registered email address. Or, Immediately sending the outgoing mail; 10. The electronic mail transmission system according to claim 9, wherein the electronic mail transmission system is set to be selectable from either one of the above.

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