Re: discarding mail during smtp session

Igor wrote:
 
>   Is it correct to reject mail (with 550 error) during SMTP?

Yes, if you are rejecting the message because you can't or won't
deliver it, and you want the sending MTA to know this.

However, most MTAs will send a 'bounce' message to the sender on
encountering a 550 reply.  For this reason, I prefer to use
'discard' rather than 'deny' in the ACL that tests for malware,
to avoid spreading the malware further.

>   Are all MTAs understand 550 error and stop trying to send same
>   letter more and more times?

Generally speaking a well-behaved MTA should not try to re-send,
since the 550 signifies a failure.  Note that this is unlikely to
be the case for an infected computer sending malware. 

--
Andrew Gay
[email protected]