I have a setup of exim4 on domain1 in front of other server, domain2 (with sendmail). Second server have no direct access to internet, so domain1 is MX for domain2. And domain2 is set as
hubbed_host in the exim4 on domain1.
When spammer sends message for no_such_user@domain2, its sendmail do a reject:
550 5.1.1 <no_such_user@domain2>... User unknown
Then, exim4 at domain1 do an auto-reply like this:
This message was created automatically by mail delivery software. A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed: no_such_user@domain2 SMTP error from remote mail server after RCPT TO:<no_such_user@domain2>: host 10.0.0.1 [10.0.0.1]: 550 5.1.1 <no_such_user@domain2>... User unknown
The spammers uses fake "from" field, and such generated messages are frozen by exim for a long time.
How can I disable some or all autoreplies from exim4? Ideally, I want a filter, if message was not delivered with error "User unknown" than don't generate any autoreply from mailer-daemon.