Anti Spam Landscape

Andy Bradford amb-plug at bradfords.org
Tue Jul 24 22:14:45 MDT 2007


Thus said Michael Torrie on Tue, 17 Jul 2007 23:22:56 MDT:

> Switch to a different greylisting daemon. If mail is being delayed for
> 24 hours, then you're doing something  wrong. I delay for a minimum of
> 20 minutes and I've never had messages delayed more than 30 minutes.

Not  necessarily.  There  are  hundreds, if  not  thousands,  of  poorly
configured mail  servers. I've been  running greylisting since  it first
came out  and this  is the  number one  problem. I  have seen  dozens of
servers that attempt  a single delivery that will bounce  on a temporary
failure (4xx  level error). I have  seen hundreds of servers  that don't
attempt delivery again for over 6 hours  and a few that attempt after 24
hours. Most problems with greylisting are on the sender side, mostly due
to misconfiguration, and often due to bad MTA software.

Another  big problem  are big  email systems  that use  a load  balanced
outgoing mail queue (gmail being the most widely known). Greylisting can
cause major headaches when receiving  emails from a domain that switches
mail servers each time it trys a redelivery.

Andy
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