The invention discloses a mail sending method and device. The device mainly comprises an attachment
processing module, an interception module, a white
list confirmation module, an invisible
watermark adding module and a mail sending module. The method mainly comprises the following steps: firstly, adding an attachment to an email and acquiring attachment content, searching keywords in the attachment content to judge and confirm whether the email needs to be intercepted or not, and then acquiring the name of an addressee email box to judge a white
list; and adding the invisible
watermark to the recipient attachment which is not in the white
list, and finally sending the new attachment to which the invisible
watermark is added to the recipient. The added invisible watermark adopts a
font transformation technology, the document content is not obviously different from that of an original document in appearance, no professional tool and
algorithm exist, watermark information cannot be modified, and the anti-counterfeiting capacity is high; watermarking information is richer and comprises information of a
receiver and a sender and sending
time information, and a document transmission path can be accurately positioned.