I have problem with configuring Sendmail, I've read a lot of topics on the net about similar problems but I didn't found a good answer for this scenario.
Main problem is that my server has poor reputation due to tons of "Unknown Users" at SenderScore.org
Scenario:
- My server receive spam emails for locally existing accounts but with prepared Return-Path headers. I want to keep them to avoid loosing emails due to false positives with SpamAssassin checks. Those emails are delivered locally without problems, but...
- Some users on my server have emails forwarding set to external servers through ".forward" file in their home directory.
- Those external servers sometimes return errors about temporary delivery problems (not important).
- My Sendmail sends such error to origin Return-Path address (these prepared).
- Because mostly those prepared addresses do not exist on those servers my server is reported as a sender of tons of mails to non existing accounts witch causes poor reputation.
About software:
- Linux Centos 6.7
- Sendmail 8.14.4
- Mails delivered locally by procmail
Questions:
Could you give me some advice how to stop these behavior?
Is there a way to discard delivery bounces produced by trying to delivery mails to ".forward" addresses?