[AusNOG] Greylisting in an ISP / Hosting Environment

Tim Warnock timoid at timoid.org
Mon Apr 27 12:06:22 EST 2009

>While it does reduce spam, you run into the problem where some ISPs and
>corporates attempt delivery from different outbound IP addresses with each
>retry period. If you are greylisting on a combination of sender IP,
>sender and envelope recipient (or even just the first two) then it's
>possible that incoming mail will be significantly delayed.

Some greylist daemons allow you to specify a subnet size to search, so if
you are being hit by several IP addresses within say a /23 it will consider
it to be from a single source.

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