Relay device

Abstract

To provide a relay device that handles the sending and receiving of emails between communication terminals within a LAN on behalf of a mail server.SOLUTION: A control unit 13 of a relay device 10 checks whether access to a mail server 30 on a communication network NW is possible, and when access is not possible, a proxy processing unit 13B performs the sending and receiving process of mail exchanged between communication terminals 20 on behalf of the mail server 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a technique for processing emails on a LAN when an external mail server cannot be accessed from the LAN. [Background technology]

[0002] When internal users belonging to a specific group in a company or organization use communication terminals connected to a LAN (Local Area Network) to exchange emails with internal users in the same group or with external users outside the group, a common configuration is to use a mail server connected to a communication network such as a WAN (Wide Area Network). In such a configuration, if a problem occurs in the mail server, the communication terminals within the LAN will be unable to send or receive emails.

[0003] Conventionally, as a technology for maintaining email processing in the event of such a failure, for example, Patent Document 1 proposes a technology in which multiple email servers are installed redundantly, and if a failure occurs in an operational email server, email processing is switched to a new email server. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-078565 Summary of the Invention [Problem to be solved by the invention]

[0005] With this type of conventional technology, if a failure occurs, the mail server is switched and email processing is handled by the new mail server, so failure of the mail server itself can be dealt with. However, if a failure occurs on the communication path between the communication network to which the mail server is connected and the LAN, access to the communication network itself from the LAN becomes impossible. Therefore, in such a case, even if the mail server is switched on the communication network, the communication network cannot be accessed from the LAN, which creates the problem of being unable to send or receive emails using communication terminals within the LAN. Another problem is that even if a user detects a failure, they cannot notify the administrator, who is an internal user, by email.

[0006] The present invention is intended to solve such problems, and aims to provide a mail proxy technology that can take over the sending and receiving of mail between communication terminals within a LAN on behalf of the mail server when a failure occurs on the communication path between the communication network to which the mail server is connected and the LAN. [Means for solving the problem]

[0007] In order to achieve this object, the relay device of the present invention is a relay device connected to a communication network and configured to relay and connect communication terminals connected thereunder via a LAN to the communication network, and comprises: a memory unit configured to store emails exchanged between the communication terminals; and a control unit configured to forward requests for email transmission and reception from the communication terminals to a mail server on the communication network, and the control unit comprises an agent processing unit that performs, on behalf of the mail server, an email sending process that stores emails exchanged between the communication terminals in the memory unit in response to an email sending request from the communication terminal, and an email receiving process that delivers emails stored in the memory unit to the communication terminal in response to an email receiving request from the communication terminal, and a relay processing unit configured to check whether access to the mail server on the communication network is possible via a communication I / F, and if access to the mail server is not possible, forward the request for email transmission and reception from the communication terminal to the agent processing unit.

[0008] In addition, one example of the configuration of the relay device according to the present invention is configured such that, during the email sending process, the proxy processing unit executes the email sending process on behalf of the internal email addresses belonging to the target domain to be processed among the destinations of the email specified in the email sending request, and skips the proxy processing of the email sending process for external email addresses that do not belong to the target domain.

[0009] In addition, in one example configuration of the relay device according to the present invention, when the relay processing unit determines that access to the mail server has been restored, the proxy processing unit is configured to execute the mail sending process for external email addresses that do not belong to the target domain.

[0010] In addition, one configuration example of the relay device according to the present invention is configured such that the proxy processing unit notifies the communication terminal that is the source of the email transmission request of the proxy status of the email transmission processing for the email. [Effects of the Invention]

[0011] According to the present invention, even if a failure occurs on the communication path between the communication network to which the mail server is connected and the LAN, the relay device performs the mail sending and receiving processing on behalf of the mail server, thereby maintaining the exchange of mail between communication terminals within the LAN. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram showing the configuration of a relay device according to this embodiment. [Figure 2] FIG. 2 is an explanatory diagram showing an example of the structure of an email address. [Figure 3] FIG. 3 is an explanatory diagram showing an example of the structure of a proxy status notification email. [Figure 4] FIG. 4 is a sequence diagram showing the operation of the relay device during normal operation. [Figure 5]FIG. 5 is a sequence diagram showing the operation of the relay device when a failure occurs. [Figure 6] FIG. 6 is an explanatory diagram showing the structure of an SMTP mail. DETAILED DESCRIPTION OF THE INVENTION

[0013] Next, an embodiment of the present invention will be described with reference to the accompanying drawings. First, a relay device 10 according to the present embodiment will be described with reference to the block diagram of FIG.

[0014] This relay device 10 consists of a relay device such as a Unified Threat Management (UTM) device or a gateway device connected to a communication network NW such as a WAN (Wide Area Network) represented by the Internet, and is configured to relay and connect a communication terminal 20 connected thereunder via a LAN (Local Area Network) to the communication network NW via a communication line L1.

[0015] [Communication terminal] Communication terminal 20 is a communication terminal such as a general PC or mobile terminal, and is equipped with applications such as a browser for accessing the Internet and a mailer for exchanging emails, in response to operations by internal users belonging to a predetermined group such as a company or organization. Hereinafter, users belonging to the above group will be referred to as internal users, and the email addresses of internal users will be referred to as internal email addresses. Users outside the above group will be referred to as external users, and the email addresses of external users will be referred to as external email addresses.

[0016] [Mail Server] The mail server 30 is a general mail server connected to the communication network NW, and is configured to perform mail sending and receiving processing for mail exchanged by users of the communication terminals 20, 40 in response to mail sending and receiving requests from the communication terminals 20 within the LAN and the communication terminals 40 outside the LAN.

[0017] [Principle of the present invention] If a failure occurs on the communication path between the communication network NW and the LAN, it becomes impossible to exchange email with communication terminals 40 outside the LAN, but communication is possible between communication terminals 20 within the LAN, so it is theoretically possible to exchange email with communication terminals 20 within the LAN. However, because the mail server is connected to the communication network NW outside the LAN, it is also impossible to exchange email between communication terminals 20.

[0018] Therefore, one possible solution to a problem occurring on the communication path between the communication network NW and the LAN is to install a mail server within the LAN. This configuration makes it possible to exchange mail between communication terminals 20 even if a problem occurs on the communication path between the communication network NW and the LAN. However, installing a mail server within the LAN increases the management workload in addition to the equipment costs.

[0019] Here, a typical LAN is provided with a relay device 10 for relaying and connecting a communication terminal 20 to a communication network NW. Furthermore, many relay devices 10 are configured to acquire and analyze various messages sent and received when the communication terminal 20 exchanges emails.

[0020] The present invention focuses on the presence of a relay device 10 in such a LAN and the configuration that the relay device 10 already has, and is configured so that the relay device 10 checks whether access to a mail server 30 on the communication network NW is possible, and if access is not possible, it performs the sending and receiving processing of mail exchanged between communication terminals 20 on behalf of the mail server 30.

[0021] As a result, even if a failure occurs on the communication path between the communication network NW to which the mail server 30 is connected and the LAN, the relay device 10 will perform the mail sending and receiving process on behalf of the LAN, so that the exchange of mail between the communication terminals 20 within the LAN can be maintained.

[0022] [Repeater] Next, with reference to the block diagram of FIG. 1, the configuration of the relay device 10 according to the present embodiment will be described in detail.

[0023] As shown in FIG. 1, the relay device 10 includes a communication I / F 11, a storage unit 12, and a control unit 13 as main processing units.

[0024] [Communication I / F] The communication I / F 11 is connected to the communication network NW via a communication line L1, and is configured to relay and connect the communication terminal 20 connected to the LAN to the communication network NW. The communication I / F 11 is also configured to take in various messages exchanged between the communication terminal 20 and the mail server 30 when sending and receiving mail, output them to the control unit 13, and relay and transfer the various messages output from the control unit 13 to the mail server 30 and the communication terminal 20.

[0025] [Storage] The storage unit 12 is generally made up of a storage device such as a semiconductor memory or a hard disk, and is configured to store various data and programs 12P used in the proxy mail processing in the control unit 13.

[0026] The program 12P is a program that realizes various processing units that execute proxy email processing in the control unit 13 by working in cooperation with the CPU of the control unit 13. The program 12P is read from an external device or a recording medium (neither of which is shown) and stored in the storage unit 12 in advance.

[0027] The main data stored in the storage unit 12 are mail data 12A and authentication data 12B. [Email data] The email data 12A is email data indicating emails exchanged between communication terminals 20, and is extracted by the control unit 13 from an email transmission request from the communication terminal 20 that is received by the communication I / F 11 and stored in the memory unit 12. [Authentication Data] The authentication data 12B is account data in which a password is registered for each email address, and is stored in advance in the storage unit 12 in response to a setting instruction from the communication terminal 20 or an administrator terminal (not shown).

[0028] [Control Unit] The control unit 13 has a CPU and its peripheral units, and is configured to realize various processing units that execute proxy mail processing in the control unit 13 by having the program 12P in the storage unit 12 and the CPU work together.

[0029] The main processing units realized by the control unit 13 are a relay processing unit 13A and a proxy processing unit 13B.

[0030] [Relay Processing Unit] The relay processing unit 13A is configured to relay and connect the communication terminal 20 to the communication network NW side by controlling the communication I / F 11, relay and forward email sending and receiving requests from the communication terminal 20 to the mail server 30, and relay and forward emails delivered from the mail server 30 to the communication terminal 20.

[0031] In addition, the relay processing unit 13A is configured to check whether or not access to the mail server 30 is possible based on the delivery status of messages such as authentication requests sent to the mail server 30, and if access is possible, to relay requests regarding sending and receiving mail from the communication terminal 20 to the communication network NW.

[0032] In addition, when an access failure occurs due to a malfunction in the communication path from the relay device 10 to the mail server 30 or in the mail server 30 itself, making it impossible to access the mail server 30, the relay processing unit 13A is configured to start proxy mail processing in the proxy processing unit 13B and transfer requests regarding mail sending and receiving from the communication terminal 20 to the proxy processing unit 13B, and then, when access to the mail server 30 is restored, to terminate proxy mail processing in the proxy processing unit 13B and relay requests regarding mail sending and receiving from the communication terminal 20 to the communication network NW.

[0033] As a result, if an access failure occurs to the mail server 30, the proxy processing unit 13B starts proxy mail processing instead of mail processing by the mail server 30. Also, if the access failure is resolved, the proxy mail processing by the proxy processing unit 13B ends, and mail processing by the mail server 30 resumes.

[0034] [Substitute processing unit] The proxy processing unit 13B is configured to perform, on behalf of the mail server 30, the following processes: an authentication process in which, in response to an authentication request from the communication terminal 20 transferred from the relay processing unit 13A, an authentication decision is made based on the authentication data 12B set in the memory unit 12, and the obtained authentication result is returned to the communication terminal 20 via the communication I / F 11 and the LAN; an email sending process in which, in response to an email sending request from the communication terminal 20 transferred from the relay processing unit 13A, emails to be exchanged between the communication terminals 20 are stored in the email data 12A of the memory unit 12; and an email receiving process in which, in response to an email receiving request from the communication terminal 20 transferred from the relay processing unit 13A, a specified email is retrieved from among the emails stored in the email data 12A of the memory unit 12, and delivered to the communication terminal 20 via the communication I / F 11 and the LAN.

[0035] In addition, during the email sending process, the proxy processing unit 13B is configured to perform the email sending process on behalf of the internal email addresses belonging to the target domain to be processed among the destinations of the email specified in the email sending request, and to skip the email sending process on behalf of the external email addresses not belonging to the target domain.

[0036] In this way, by distinguishing destination email addresses based on the target domain, it is possible to very easily select destination email addresses that can be processed for sending.

[0037] The example of an email address configuration shown in Figure 2 shows the username and domain name that make up the email address. For example, in the case of the email address "kenta@saxa.jp", the username is "kenta" and the domain name is "saxa.jp". Similarly, in the case of the email address "takashi@saxa.jp", the username is "takashi" and the domain name is "saxa.jp". On the other hand, in the case of the email address "catherine@shirokane.jp", the username is "catherine" and the domain name is "shirokane.jp".

[0038] Therefore, when an access failure occurs, for example, if a mass email is sent from the sender "kenta@saxa.jp" to the destinations "takashi@saxa.jp" and "catherine@shirokane.jp," proxy processing unit 13B will proxy the email sending process for the destination "takashi@saxa.jp," which includes the sender's domain name "saxa.jp," and will skip proxying the email sending process for the destination "catherine@shirokane.jp," which does not include the sender's domain name "saxa.jp."

[0039] As a result, in the mail transmission process, only internal mails having a deliverable internal mail address as a destination are stored in the mail data 12A of the storage unit 12, and the storage of external mails having an undeliverable external mail address as a destination can be avoided, thereby enabling the storage capacity of the storage unit 12 to be used effectively.

[0040] Furthermore, the proxy processing unit 13B is configured to notify the communication terminal 20, which is the request source of the email transmission request, of the proxy status of the email transmission process for the email to be processed during email transmission processing. The proxy status may indicate whether transmission was successful or unsuccessful for each email address specified as the destination, and may be notified to the communication terminal 20, which is the sender, by email, or to an application such as a browser or email client.

[0041] In the example of the proxy status notification email shown in Figure 3, the email body contains information that the relay device 10 is performing proxy email processing due to an access failure, a summary of the email requested by the user to be sent, and the status of the proxy email sending process.

[0042] The email sending process status in Figure 3 shows the email sending process status when a mass email is sent from the sender "kenta@saxa.jp" to the recipients "takashi@saxa.jp" and "catherine@shirokane.jp." As a result, the user is notified that the email was successfully sent to the internal email address "takashi@saxa.jp," but failed to be sent to the external email address "catherine@shirokane.jp."

[0043] [Operation of this embodiment] Next, the operation of the relay device 10 according to this embodiment will be described. The following describes an example in which communication terminal A (20) sends a broadcast email addressed to communication terminal B (20) and communication terminal X (40). Normally, the destination of an email is specified by an email address, but in this embodiment, for ease of understanding, it is assumed that there is a unique correspondence between the email address and the communication terminals 20 and 40, and the destination of an email may be expressed by the communication terminal.

[0044] [During normal operation] First, referring to the sequence diagram during normal operation shown in Figure 4, we will explain the email sending and receiving operation during normal operation when no access failure occurs due to a malfunction in the communication path from relay device 10 to mail server 30 or in mail server 30 itself.

[0045] In response to a user operation, an authentication request sent from communication terminal A is received by relay device 10 via the LAN, and is relayed and transferred to mail server 30 via communication line L1 and communication network NW (step 100).

[0046] In response to this, the authentication result sent from the mail server 30, in this example authentication success, is received by the relay device 10 via the communication network NW and communication line L1, and is relayed and forwarded to communication terminal A via the LAN (step 101).

[0047] Next, the mail sending request for mail (broadcast mail) sent from communication terminal A and addressed to users of communication terminals B and X is received by relay device 10 via the LAN and relayed to mail server 30 via communication line L1 and communication network NW (step 102).

[0048] In response to this, the mail server 30 executes a mail sending process to store the mail for each destination of the mail (step 103).

[0049] As a result, when the user of communication terminal X performs an operation to receive mail, first, an authentication process is executed between communication terminal X and mail server 30 via communication network NW (steps 110 and 111), and depending on the authentication result obtained, in this example, authentication success, a mail reception request is sent from communication terminal X to mail server 30 via communication network NW (step 112).

[0050] In response to this, the mail server 30 retrieves the mail addressed to the communication terminal X specified in the mail reception request from among the stored mails, and returns a mail reception response to the communication terminal X via the communication network NW (step 113). This allows the user of the communication terminal X to view the contents of the mail.

[0051] Furthermore, when the user of communication terminal B performs an operation to receive mail, first, an authentication process is executed between communication terminal B and mail server 30 via the LAN, relay device 10, and communication network NW (steps 120, 121), and depending on the authentication result obtained, in this example, authentication success, a mail reception request is sent from communication terminal B to mail server 30 via the LAN, relay device 10, relay device 10, and communication network NW (step 122).

[0052] In response to this, mail server 30 retrieves the mail addressed to communication terminal B specified in the mail reception request from among the stored mails, and returns a mail reception response to communication terminal B via communication network NW, relay device 10, and LAN (step 123). This allows the user of communication terminal B to view the contents of the mail.

[0053] [When a failure occurs] Next, referring to the sequence diagram when a failure occurs shown in Figure 5, we will explain the email sending and receiving operation when a failure occurs, in which an access failure occurs due to a problem in the communication path from the relay device 10 to the email server 30 or in the email server 30 itself.

[0054] In response to user operation, the authentication request sent from communication terminal A is received by relay device 10 via the LAN, and is relayed from relay device 10 to mail server 30 via communication line L1 and communication network NW (step 150).

[0055] If a failure occurs and no response is received to the authentication request, the control unit 13 of the relay device 10 determines that access to the mail server 30 is not possible using the relay processing unit 13A, and starts proxy mail processing in the proxy processing unit 13B (step 151). From this point on, various requests related to sending and receiving mail from the communication terminal 20 are transferred to the proxy processing unit 13B.

[0056] In response to the authentication request from communication terminal A transferred from relay processing unit 13A, proxy processing unit 13B confirms the authentication based on authentication data 12B in memory unit 12 and returns the authentication result, in this example, authentication success, to communication terminal A via the LAN (step 152).

[0057] In response to this, the mail transmission request for mail (broadcast mail) sent from communication terminal A and addressed to users of communication terminals B and X is received by relay device 10 via the LAN (step 153). Substitution processing unit 13B distinguishes the destinations of the mail and performs mail transmission processing for mail addressed to communication terminal 20 within the LAN (step 154).

[0058] 2, the proxy processing unit 13B distinguishes between internal email addresses belonging to the target domain to be processed and external email addresses that do not belong to the target domain among the destinations of the email specified in the email transmission request, generates an internal email based on the email and sends it to the internal email address, while skipping the proxy processing of email transmission for external email addresses.

[0059] As a result, the internal emails are stored in the email data 12A of the storage unit 12 by the proxy processing unit 13B in association with the internal email addresses set as destinations.

[0060] When SMTP (Simple Mail Transfer Protocol) is used as the mail transmission protocol between the proxy processing unit 13B and the communication terminal 20, the RCPT command may be used as one of the processes for generating internal mail.

[0061] As shown in Figure 6(a), an SMTP email consists of an envelope section 200 that indicates various SMTP commands, and an email data section that consists of an email header 201 and an email body 202. The email destination is written in the "To" field of the email header 201, but the SMTP RCPT command can be used to specify an email destination that takes priority over the "To" field.

[0062] Therefore, if you want to send the original email to only internal email addresses in the proxy processing unit 13B, you can simply specify only the internal email addresses in the RCPT command, as shown in the envelope part 210 in Fig. 6(b). This makes it easy to create an internal email that will be delivered only to internal email addresses, without modifying the original email.

[0063] Thereafter, the proxy processing unit 13B notifies the communication terminal A, which is the request source of the email transmission request, of the proxy status of the email transmission process for the email to be processed (step 155). As a result, as shown in Fig. 3 above, the user is notified that the email transmission to the internal email addresses among the destinations has been successful, but that the email transmission to the external email addresses has failed.

[0064] Therefore, thereafter, when the user of communication terminal B performs an operation to receive an email, first, an authentication process is executed between communication terminal B and the proxy processing unit 13B of the relay device 10 via the LAN (steps 160 and 161), and depending on the obtained authentication result, in this example, successful authentication, a request to receive an email is sent from communication terminal A to the relay device 10 via the LAN (step 162).

[0065] In response to this, proxy processing unit 13B of relay device 10 retrieves the mail addressed to communication terminal B specified in the mail reception request from among the mails stored in mail data 12A of storage unit 12, and returns the mail reception response to communication terminal B via the LAN (step 163). As a result, the user of communication terminal B can view the mail content.

[0066] After this, in response to a user operation, for example, when an authentication request for sending and receiving mail is sent from communication terminal B, the request is relayed from relay device 10 to mail server 30 via communication line L1 and communication network NW (step 170).

[0067] If the failure has been resolved and a response to the authentication request is returned from mail server 30 (step 171), control unit 13 of relay device 10 determines that relay processing unit 13A can access mail server 30, and terminates the proxy mail processing in proxy processing unit 13B (step 172). As a result, from this point on, relay device 10 returns to the normal operation described above, and relays and transfers various requests related to sending and receiving mail sent from communication terminal 20 to mail server 30 via communication line L1 and communication network NW.

[0068] [Advantages of this embodiment] In this manner, in this embodiment, in the control unit 13 of the relay device 10, the relay processing unit 13A checks whether or not access to the mail server 30 on the communication network NW is possible, and if access is not possible, the proxy processing unit 13B is configured to proxy the sending and receiving processing of mail exchanged between the communication terminals 20 on behalf of the mail server 30.

[0069] As a result, the relay device 10 performs the process of sending and receiving emails on behalf of the mail server 30, so even if a failure occurs on the communication path between the LAN and the communication network NW to which the mail server 30 is connected, it is possible to maintain the exchange of emails between the communication terminals 20 within the LAN. Furthermore, when a user detects a failure, the administrator, who is an internal user, can be notified by email, enabling the administrator to begin responding to the failure at an early stage.

[0070] [Extended embodiment] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0071] In the above embodiment, the proxy processing unit 13B performs the authentication process, the email transmission process, and the email reception process, but this is not limiting. For example, the authentication process, the email transmission process, and the email reception process may be divided and executed by multiple proxy processing units. This allows the processing load to be distributed, and requests from the communication terminal 20 can be handled smoothly.

[0072] In the above embodiment, the proxy processing unit 13B distinguishes between email addresses to be processed for email transmission from the destinations of the email specified in the email transmission request based on the domain name of the email address, but this is not limited to this. For example, email addresses to be processed for email transmission may be registered in advance as a list in the storage unit 12, and whether or not to process the email may be determined based on whether or not the email address is registered in the list. Furthermore, since the authentication data 12B in the storage unit 12 includes email addresses, this may be used as the list.

[0073] Furthermore, in the above-described embodiment, relay processing unit 13A determines that access to mail server 30 is not possible if, as a result of sending an authentication request to mail server 30, no response to the authentication request is returned, but relay processing unit 13A may be configured to determine whether access to mail server 30 has been restored by continuously sending authentication requests to mail server 30. If relay processing unit 13A determines that access to mail server 30 has been restored as a result of continuously sending authentication requests, proxy processing unit 13B may perform mail sending processing for external mail addressed to an external mail address that does not belong to the target domain of the internal mail address. [Explanation of symbols]

[0074] 10... relay device, 11... communication I / F, 12... memory unit, 12A... email data, 12B... authentication data, 12P... program, 13... control unit, 13A... relay processing unit, 13B... proxy processing unit, 20, A, B... communication terminal, 30... mail server, 40, X... communication terminal, L1... communication line, LAN... local communication network, NW... communication network.

Claims

1. A relay device connected to a communication network and configured to relay and connect a communication terminal connected thereunder via a LAN to the communication network, a storage unit configured to store emails exchanged between the communication terminals; a control unit configured to transfer a request for sending and receiving mail from the communication terminal to a mail server on the communication network; The control unit an agent processing unit that executes, on behalf of the mail server, a mail sending process that stores mail exchanged between the communication terminals in the storage unit in response to a mail sending request from the communication terminal, and a mail receiving process that delivers mail stored in the storage unit to the communication terminal in response to a mail receiving request from the communication terminal; a relay processing unit configured to check whether or not a mail server on the communication network can be accessed via a communication I / F, and if access to the mail server is not possible, to transfer a request for sending and receiving mail from the communication terminal to the proxy processing unit; A relay device comprising:

2. 2. The relay device according to claim 1, The relay device is characterized in that, during the email sending process, the proxy processing unit performs the email sending process on behalf of the internal email address belonging to the target domain to be processed, among the destinations of the email specified in the email sending request, and is configured to skip the proxy processing of the email sending process for external email addresses that do not belong to the target domain.

3. 3. The relay device according to claim 2, When the relay processing unit determines that access to the mail server has been restored, The relay device is characterized in that the proxy processing unit is configured to execute the email sending process for external email addresses that do not belong to the target domain.

4. The relay device according to any one of claims 1 to 3, The relay device is characterized in that the proxy processing unit is configured to notify the communication terminal that is the source of the mail transmission request of a proxy status of the mail transmission processing for the mail.

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