[vox-tech] postgrey is dangerous?

[Troy Arnold]

On Sun, Jun 29, 2008 at 04:17:38PM -0700, Tony Cratz wrote:
> 
> 	So the bottom line is, using Postgrey now is just a waste of
> 	computer resources and time. 


Not at all true.  Have you actually run a greylisting system?  Tracked the
spam volume before and after?  I'm responsible for mail services for a
small web-dev and hosting company.  Our numbers show a typical mailbox
getting roughly 5 percent as much crap through.  Since this crap is then
run through spamassassin, the greylisting is a huge net *reduction* in CPU
(for our side; the sender, of course has some extra overhead).

Because of the (first time) several minute delay due for new senders, we
allow folks to disable greylisting for whole domains or individual
mailboxes.  Although several clients experimented with disabling it, we
currently have have 4 (out of 273) boxes and zero domains that have opted
out.  

That said, it does take some vigilance to run a greylisting system well.
One needs to keep an eye on the logs to catch any systems that need
exceptions.  (Places with big SMTP server farms like IBM or Google, or
systems that for whatever reason take a TEMPFAIL as a FAIL.)

I've run a couple of different greylisting patches for qmail as well as
postgrey.  Postgrey/postfix is by far my favorite.

-t