Sorry, let me express it more clearly. The problem has nothing to do with e-mail server, I think. what I want to do is to get the mail information when the users send their mails on this compute.
when a user is sending a mail, then there should be a TCP connection to the e-mail server, maybe we should get these TCP packets through the connection by using libpcap , then parse the packets, we can get what I want.
But this method is a little fussy, so do you have better solution?