It's my understanding that if we use :fail: as the default address for a domain, then junk to that domain will be blocked from even comming into the server.
It's worked like this for years.
So if domain xxyz.com used :fail: no Such User Here
Why do I have a bunch of undeliverable emails in my queue that say:
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 Here
I am using a standard Exim configuration, plus I've added "Mail Manage" and "Mail Queues" from ConfigServer