rejecting spam at SMTP time (was Re: Postfix anti-antivirus (was Re: [linux-elitists] etc))

George Georgalis george@galis.org
Fri Sep 24 06:57:35 PDT 2004


On Fri, Sep 24, 2004 at 07:40:38AM -0500, Rob McGee wrote:
>
>On Thursday 23 September 2004 13:56, George Georgalis wrote:
>
>> 1 While spammers may get to know what gets rejected with SMTP-time
>> filters, so do legitimate senders, which I take as a big positive vs
>> legitimate mail being dropped (or returned, which is likely to also
>> mean forged address are getting reject messages).
>
>Forged messages become the sending MTA's problem. This is the biggest 
>problem I see in qmail: accepting all that mail and all those problems, 
>which rightfully belong with the sending MTA.
>
>http://www.postfix.org/BACKSCATTER_README.html
>

I filter/reject (and stop processing) spam in SMTP before I check
if a user is known. Just like virus filtering, there is no sense in
responding (rejecting) to anything but the computer initiating the
delivery.


>> 2 If rejected messages are also queued, users can certainly review
>> rejected messages with webmail, I've not bothered to sort them by
>
>I barely have time for real mail and lists as it is! IMO the best thing 
>to do is to provide informative rejection messages and a Web contact 
>form, so legitimate non-automated senders have a way of telling you 
>they were rejected.

yes, also,

rejecting spam in smtp lowers the value of the address for address
re-sellers, as does reporting to their provider or upstream, it would
seem. Purely imperial, but given the number of spam I receive, it think
spammers do pay attention to rejections and abuse reports, at least some
of them.

// George

-- 
George Georgalis, systems architect, administrator Linux BSD IXOYE
http://galis.org/george/ cell:646-331-2027 mailto:george@galis.org



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