OT: Sendmail REJECT or DISCARD preference

Steve Freegard steve.freegard at fsl.com
Mon Mar 31 23:48:53 IST 2008

Peter Farrow wrote:
>> Yes there is.
>> You accepted the first message, the one later rejected. You passed
>> that through MailScanner. You passed it on to your "unsuspecting
>> client", who _then_ rejected it.
>> If you had called ahead _prior_ to passing the first message
>> intoMailScanner you would've avoided ever handling the message....
>> Past the initial reject.
>> So you spend a few resources, you gain a lot of resources (never
>> used.... Remember that MailScanner is pretty hungry, compared to an
>> address verification call).
>> When you get hammered with a so-called dictionary attack, joe-job or
>> whatever... this will count.
>> Cheers
> Nope, I discarded before it got to the mailscanner, before mailscanner 
> even touched it to forward it to the client server, becuase I implement 
> a discard list for known spammers I don't discard stuff I've previously 
> accepted...

What about the spammers you don't yet know about?  It's hardly a static 

Whenever you accept a message for a user that doesn't exist at the 
remote SMTP server, you've wasted your resources as you've had to virus 
scan and SpamAssassinate it, then if the remote SMTP server rejects the 
message with a '550 Unknown User' at RCPT TO time, then *your* SMTP 
server has responsibility for generating a DSN back to the sender, which 
is far worse as it makes you generate backscatter to the rest of the 
internet.  If the remote SMTP server doesn't reject, but accepts the 
message - then it generates the backscatter (as it's 
accept-then-bounce), either way - that's bad.


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