Matthew Bickerton wrote:
I have been thinking about implementing Greylisting. However, I am worried about blocking/long delays with e-mails from mail farms (gmail, yahoo etc.)
You could compromise by greylisting based on blocklists (such as spamhaus, etc.). This would free up some resources by rejecting a fair amount of mail that would otherwise go to spamassassin. For my setup (consisting of two users), greylisting with this method eliminates half of spam that would have otherwise gone to spamassassin. (about 250/500 per week). It also means that you can greatly increase the greylist time to several hours or even a day since it would be unlikely that legit e-mail would be greylisted, but if it was it would still get through, although quite delayed. Of course if you are using blocklists for blocking...then that wouldn't help.
You can also add a whitelist to bypass the greylisting for large mail servers.
Personally, I didn't like the added delay for first-time mails, which is why I chose to greylist only on blocklists, but for a minimal effort my spam was significantly reduced.
Hope that helps. -- Chris
