sender verification

[Jan-Peter Koopmann]

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Hi Jim,

> Yes, I realise that, but that is not what I am looking for,
> as blocking mail at the SMTP stage could lead to unacceptably
> high rejection rates of legitimate mail.  

Not necessarily. Depends on your setup.


> That is why I would
> like to see this being implemented after receipt of the
> message - just as DNSBL and other checks are carried out
> afterwards by MailScanner.  

I use DNSBL at MTA level and with SpamAssassin. If the IP triggers one of two RBLs I trust the message is rejected. If it hits one of several other RBLs I slow down the SMTP protocol (enforcing synchronization) and catch quite a lot of spam with that. Then later on I let SpamAssassin do the rest.

> It means that retrieval from
> quarantine, and whitelisting of specific addresses could be
> implemented consistently with other MailScanner features.

To be honest: I would think of this as unneccessary overhead. Why don't you simply verify the sender address at MTA level, add a header to the message in case the verify fails and then write a simple SpamAssassin rule for this? That's what we do here. It's quick and no code has to be changed. I'm not sure how easy this is with sendmail but with exim this is a matter of minutes.

New code in MailScanner only brings the possibility of new errors as the code gets more and more complex, especially since the feature you want would mean implementing/using SMTP. The only advantage would be that people not using SpamAssassin could use this functionality. I doubt there are many people out there that fit this definition though. :-)

Regards,
  JP

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