I would like to stop all mail from going to one of my domains. This domain is purely a website and has no MX record. The problem is that spammers are sending mail to the domain and it causes Spamassassin and Clamav to use system resources. Sometimes the spam makes it through and I get it via my catchall account. Is there a way to quietly discard all mail sent to a domain or maybe block ports 25, 110 & 143 for a single domain? Another option would be if I could block all incoming mail except from specific IP addresses. We have a external service that filters all of our incoming mail. We use their domain in our MX record already but it does not cover all of my domains. Today my Postfix mailqueue went up to levels I have never seen and both Spamassassin and Clamav are going crazy using resources. It appears I am under some sort of DDOS attack via mail.