Nolisting: Poor Man's GreylistingWhat is it? Nolisting reduces the amount of fire-and-forget spam an MTA must process by specifying a primary MX that is always unavailable. Is it the same as greylisting? No, but it exploits the same noncompliant behaviour of spamware and viruses, including those that spread via internal SMTP engines. Greylisting is an approach promoted and rigorously tested by Evan Harris. It is sensible, RFC-com
