Turn off Postgrey for 1 domain?

[motokochan]

NetworkExpertise Wrote:I have a customer complaining that his clients cannot email them because their PTR records are incorrectly setup so its blocking important email. Is this postgrey even a good solution to spam filtering? It seems to do more harm then good.

Postgrey doesn't care what the PTR is on an IP, all it does is temporarily slow delivery the first time a mail arrives from a specific sender. What makes your client think postgrey is the problem?

Postgrey and greylisting in general are okay methods for dropping some spam. It was developed because a lot of the spam relays installed on compromised computers didn't follow standard mail practice and retry after a temporary (4xx) error.

The benefit is that if you provide a temporary error when being sent a mail the first time, this spam wouldn't ever reach your server. At the beginning, this dropped spam volumes about 60 - 80% in general. Newer spamming software is wise to this trick and actually will follow proper behavior, making this less effective, but a decent amount of spam is still being sent with the broken software. This lower volume means less spam to actually work your server CPU on, and increases the volume of mail throughput. It also lets you tune your filters to better fit the spam that does get through while not worrying about that other stuff.