Question Outgoing email filtering by domain

[Aristeidis Vlachopanos]

Hello,

I recently took over the administration of a Debian server running Plesk 12.5 with qmail as the mail server. I have no previous experience on the specific configuration but I noticed that there are emails in the mail queue with domains other than ours (i.e. from yahoo or gmail). An example:

Received: (qmail 16656 invoked from network); 7 Oct 2017 12:38:53 +0300
Received-SPF: pass ("mydomain": domain of yahoo.com designates 77.238.177.33 as permitted sender) client-ip=77.238.177.33; envelope-from="random-address"@yahoo.com; helo=sonic310-12.consmr.mail.ir2.yahoo.com;
Received: from sonic310-12.consmr.mail.ir2.yahoo.com (77.238.177.33) by "mydomain" with (AES128-SHA encrypted) SMTP; 7 Oct 2017 12:38:52 +0300

I am suspecting that these messages have a negative effect on the server's reputation.

Is there a way to filter the mail messages by domain before they are queued and limit the outgoing traffic only to our domains?

The rcpthosts file is set but it doesn't seem to effect these emails.

Thank you.

 

[Bitpalast]

Such outgoing mails are normally created by forwarding rules in customer accounts. Some customers, for example, forward all their incoming mail to their Yahoo or Gmail accounts. They should not do that, but use the POP3 collection services of the third-party mail providers, instead. Nevertheless, they forward everything. And indeed, these forwards have an extremely negative impact: All spam is forwarded, too, so that Yahoo instantly puts the IP address of the server on a black list now blocking all traffic from the server to Yahoo.

Unfortunately, there is no good method to selectively stop forwarding.