Adding Greylisting To A FreeBSD Postfix Mail Server | Development-CycleGreylisting is an important tool in the war against spam, servers who connect to a mail server with an active greylisting are given a 450 recipent address rejected error the first time they try to connect and will not be allowed to successfully connect for a predefined time frame (normally a couple of minutes). A 450 SMTP error is not a permanent error and an RFC compliant mail server will try a
