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: firstname.lastname@example.org No Such User Here I am using a standard Exim configuration, plus I've added "Mail Manage" and "Mail Queues" from ConfigServer Any suggestions?