Returned e-mail I didn't send

[rando1000]

I run out company's e-mail server, a Fedora 7 machine running postfix/dovecot. I've been getting a few undeliverable messages in various users inboxes for messages they did not send. I've double checked the log file, and no messages went out to the intended recipient from our server. I've checked for open relay, and all tests come out negative.

I'd guess that it's just someone randomly creating their reply-to line, except that the reply-to is a legitimate user and our domain, and the from line uses the same user name but a different domain.

Any ideas what might be happening? I'm pretty sure it's not my server, since there is nothing in the log.

[sicarie]

Are these SPAM messages, perchance?

I know that I have gotten more than a few SPAM email messages that were returned to (or sent by) me - I'm not sure how they spoof the sender, but if they have your email, it can be done.

[micmast]

most likely those are indeed returned spam messages, since it would seem weird. If however somebody is trying the sending an email to an invalid user ip gathering technique, they are doing it wrong :)

btw spoofing an email is as easy as drinking a glass of water:

telnet something.server.com 25
> HELO something.server.com
> FROM: [e-mail]
> RCPT TO: [e-mail]
> DATA
All the data here :)
.

> QUIT

done :)