Re: Initial Installation Step 2

[Andrew Daviel]

On Thu, 25 Jun 2009, Don Armstrong wrote:

> [Though in reality, you should really just discard spam messages
> instead of rejecting them.]

The whole point of a milter IMO is that you can reject suspicious mail 
without your MTA generating a message back to a probably bogus return 
address.

If the mail is genuine, but the sender has done something like send a big 
attachment with no content, or sent a virus sample, then their MTA sends 
then a nondelivery message which includes the text string from the error 
status. If they actually read it (unlikely), it will tell them why their 
mail was not delivered.

If the mail is sent from a direct-to-MX botnet, chances are the agent 
ignores the error status entirely. (Having the address flagged as 
undeliverable would be too much to hope for).

On the other hand, giving success status to all mail might encourage 
SMTP scanners to think the address is valid and add it to mailing lists.


--
Andrew Daviel, TRIUMF, Canada
Tel. +1 (604) 222-7376  (Pacific Time)
Network Security Manager