Milter-greylist

> From: milter-greylist@yahoogroups.com
[mailto:milter-greylist@yahoogroups.com] On Behalf Of Les Mikesell
> Sent: Thursday, February 17, 2011 6:54 PM
> To: milter-greylist@yahoogroups.com
> Subject: [milter-greylist] Can milter-greylist run after sendmail checks
users?


  

> I am running sendmail/MimeDefang and recently added milter-greylist as 
> an additional spam check. The domains in question are regularly hit with 
> dictionary-attack type spam where most of the target users don't exist. 
> Sendmail is very quick at rejecting local addresses that are not in 
> the aliases or virtuser tables so that is normally not a problem, but 
> when milter-greylist is active it wants to greylist even the 
> undeliverable addresses. For the moment I am working around it by 
> tracking the 'real' users, including them in the milter-greylist config, 
> and restricting greylisting to the specified addresses. However, it 
> would be nicer if this could be handled automatically by letting 
> sendmail reject addresses it can't deliver first. Is there any way to 
> do that?

> Also, the extra log line about 'skipping greylist because this is the 
> default action' for the unprocessed addresses is filling my disks up to 
> the point that I had to change the log rotation. Is there any way to 
> turn that off? When it doesn't do anything, I don't need to know about it.

> -- 
> Les Mikesell
> lesmikesell@... <mailto:lesmikesell%40gmail.com> 

Ok., it's a week since you asked, but here are some ideas 
about the way greylisting works. Hopefully I did not get 
it all wrong.

If you run greylisting *before* user check, it won't make any 
difference, as the trick is, that the same combination of
sender IP, sender & recipient address "never" comes again in 
a SPAM message.

Also, if you are sending out non-deliverable-messages for 
nonexistant recipients: on SPAM they will either be bounced
(because the sender does not exist) or reach somebody innocent.

So I believe it is better to block SPAM with greylisting before
checking valid users. The only "problem" may be you are blowing 
up the greylisting database.

Just my 2cc, Wolfgang Steger
 
-- 
  Dipl.Ing. Wolfgang Steger        first facility GmbH
  IT Server Management             a member of EVN Group
  wolfgang.steger@... 1120 Wien, Technologiestr. 8
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