[nSLUG] Whither to bounce unknown recipient address?

Dop Ganger nslug at fop.ns.ca
Thu Aug 30 13:28:58 ADT 2007

On Thu, 30 Aug 2007, D G Teed wrote:

> I'll have to convince people setting
>   unknown_local_recipient_reject_code = 550
> in postfix is a good idea.
> How many of you use this (or similar) in your MX server?

I use recipient verify, which is (if I'm reading correctly) the same thing 
for Exim. A lot of spammers trip themselves up right at HELO, though; 
here's stats for mail for fop.ns.ca for yesterday:

Mail log summary from 2007-08-29 06:29:36 to 2007-08-30 06:59:21:

1 rejected with HELO of speedtouch.lan
2 rejected with unqualified FQDN with strange characters
5 rejected by SURBL
17 rejected with HELO of localhost
21 rejected with delivery to unknown address
94 deferred by greylist
121 rejected from known dynamic IP address
123 rejected with malformed HELO

24 warning flags set
391 mails rejected outright
485 mails rejected or deferred
371 sessions dropped by remote sender
590 mails accepted for delivery

I prefer to reject mail at SMTP time simply because it means less 
processing on the backend - and when the backend is a 100MHz PA-Risc box, 
it needs to do as little processing as possible...

Cheers... Dop.

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