My users have setup many email forwards

The SPAM emails also get forwarded

Due to this, email providers like microsoft / gmail are rate limiting emails from my servers and also blacklisting the IP

How to stop my server forwarding SPAM

I have enabled

ClamAV, Amavis & Spamassassin

It is not feasible to disable these redirects.

So, you can do what I do: use a global antispam system on your server, where you can use postscreen, and use a system (Spamassassin, Rspamd, etc) that performs Bayesian analysis of emails (there will be complaints, globally means spam for some, but not for others). But Bayesian analysis learns fast, before problem turn big. Rspamd have neural analisys, too.

In addition, monitor rejections from major providers: Gmail, Outlook (mainly Hotmail), etc. When there are problems with these major email providers, they complain first with error messages, and gradually lowering reputation of your mail server. With active monitoring, you will have enough time to avoid a definitive block on them, and you will have time to complain about the redirection of your clients, or even disable them.

Regards,

Netino

Edited May 23May 23 by Netino

On 5/23/2025 at 5:38 AM, Netino said:

It is not feasible to disable these redirects.

So, you can do what I do: use a global antispam system on your server, where you can use postscreen, and use a system (Spamassassin, Rspamd, etc) that performs Bayesian analysis of emails (there will be complaints, globally means spam for some, but not for others). But Bayesian analysis learns fast, before problem turn big. Rspamd have neural analisys, too.

In addition, monitor rejections from major providers: Gmail, Outlook (mainly Hotmail), etc. When there are problems with these major email providers, they complain first with error messages, and gradually lowering reputation of your mail server. With active monitoring, you will have enough time to avoid a definitive block on them, and you will have time to complain about the redirection of your clients, or even disable them.

Regards,

Netino

I see some hints at https://talk.plesk.com/threads/do-not-forward-spam-emails-to-external-mailbox.370124/

Using postfix-pcre to block outgoing emails with SPAM in subject line

Have implemented the same.

Hope it works, I will update it here.

Email messages are essentially text messages. When you install postfix-pcre, it will perform a regex analysis on each message, and this involves additional processing. If you have a small volume of messages on your mail server, this is fine, there should be no problem. But if your traffic is heavier, I recommend that you do a performance analysis, and if there is an impact, find a less expensive solution.

As of now I am able resolve the issue by

Solution:
Step 1: Made sure that SPAMAssassin is working. https://forum.centos-webpanel.com/e-mail/how-to-install-spamassassin-updated/msg51428/#msg51428 and other threads

Step 2: Added outgoing email filter to block emails with subject SPAM https://talk.plesk.com/threads/do-not-forward-spam-emails-to-external-mailbox.370124/

This is working very well now.