Greylisting isn't a spam term
Are you now the arbiter of the spam glossar? Say "greylisting" to any serious MX admin, and he knows you're talking about an anti-abuse tactic.
(due to abuse; many different people have come up with many different definitions for "greylist").
Here's the one implemented by postgrey for postfix (simplified):
Each never-seen triplet of IP+sender+recipient is 450 rejected for <greylist> period.
Every triplet that is retried after the greylist period is accepted (by greylist function, but subject to all other filtering) and is cached (for x days) so the triplet never has to be greylisted again (unless its cache item expires).
Legit MTAs sail right through greylisting because they always retry. Legit senders of correct MTAs never see the 450 reject.
zombied/ratware/compromised mailing PCs don't retry after 4xx reject, so greylisting them is effectively blacklisting them.
For an MX that has been running greylisting several weeks, for first 9 hours of Monday:
========================= Postgrey Greylist Rejects ========================= Total: 46568 Net : 32847
That's 33K triplets that weren't retried (effectively blacklisted), while 47K - 33K = 14 K triplets were retried and accepted. 33K is about 25% of total rejects.
Len
_____________________________________________________________________ http://IMGate.MEIway.com : free anti-spam gateway, runs on 1000's of sites
To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/
