Why is the mail-server sending a copy of a message to wrong recipients?

We’re using MDaemon 10 as the mail-server software. The serious issue with it is that, it sometimes, and quite randomly, send a copy of a message to one or more wrong random recipients who have nothing to do with the message. Any help? Thanks.

The log says it went to recipient x but it went to y, too. The mail headers show it came directly to recipient y. The are no .forward files, nor any other automated forwarding systems, and users are not BCC-ing one another. Outlook Connector is known to cause this particular problem, but that’s not the cause with me. I also asked at altn.com and at Server Fault, but this didn’t help.

To answer some questions:

Could you ask one of the random
recipients to forward you the full
source of the email they received? And
how does that compare to what’s in
your own log files?

I’ve seen the source of one of those random emails, the source looks like the sender sent the random recipient the email directly, but my log doesn’t contain information about such a communication between the sender and the random recipient (recipient y).

How “random” are these recipients?
(Like: do you know them? Are the
domain names different?)

All the addresses are in the same domain, and people in the company are telling about the random emails they’re getting, so the server contains no information that tells about that issue.

Are these people in the To: or Cc:
list, or are those Bcc-copies?

They’re in the “To” of the message, as if the message is sent to them directly, just like the right recipient.

Does it happen for all Senders, or
just some people?

It happened with some of the senders, as it happens occasionally and quite randomly.

What did you already investigate?

  • I’ve seen the settings of the mail-server software (MD) and didn’t found anything that causes that issue to happen, so no forward rules or anything.
  • The log files don’t tell anything about the problem.
  • The source of the random email doesn’t contain any helpful info, it looks quite innocent and is quite similar to the right email.

Answer

Are you certain that the mail came directly from the server to “recipient y”? Perhaps it was only sent to “recipient x”, but “recipient x” somehow forwarded the message to “recipient y”?

Examine the headers of the email received on both systems to determine the path the email took.

Attribution
Source : Link , Question Author : Moayad Mardini , Answer Author : Brent

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