I have a client who has about half of their accounts migrated to an internal mail platform on a different domain name. To maintain continuity, they have accounts for all of these on my Smartermail server on their public domain but set to forward mail to their other domain.
So for example, email@example.com forwards email to firstname.lastname@example.org.
The issue I've been running into is that some of their accounts on my system have been receiving a fair volume of spam, which is then forwarded to their other email address, and that server is rejecting the message due to being potential spam, so it sends a bounce back to my server, which then tries to forward the bounce to the spammer/sender. And because those accounts are often not real, this causes mail to build up in my spool as it goes through the retry process.
Is there any way to disable forwarding bounces via forwarder accounts?