[Mimedefang] Rejecting spam - users unsubscribed from distribution lists

[Paul Murphy]

Joseph,

>>> On 25 October 2006 at 14:18, Joseph Brennan <brennan at columbia.edu> wrote:
>With Mimedefang or any milter, you should be refusing.  If you accept
>and then decide later to generate and mail a bounce, that's the cause
>of many problems just as stated above.

There are three options in MIMEDefang:

1.  Accept
2.  Reject
3.  Discard

The fact that the Reject option is called action_bounce() does not help to make things clear.

A bounce message is only generated if the mail server has accepted a message and then been unable to deliver it.  The whole point of any milter is to do the processing during the SMTP conversation, which allows you to accept or reject the message during the conversation.

I choose to *discard* because that is my policy - reject pushes the problem back to the connecting server, which in 90% of cases does nothing with it because it is a spambot, but in the 10% where it is indeed a valid server which has incorrectly accepted the message for onward delivery, it then generates a bounce to the stated sender, which is normally spoofed anyway.  We then get contacted by the owner of the spoofed address asking why our system is claiming to have rejected a message from them when they know they haven't sent one, and my support load goes up as a result.

Every site has its own policy, which is one of the benefits of using MIMEDefang it allows a plethora of policies, all subtly different.  The original poster asked for advice, and discarding spam rather than telling the sender they sent it is infinitely preferably to trying to work out whether to send a 5xx reject return code or not, as your 5xx code will almost certainly be ignored for spam.

Best Wishes,

Paul.
-- 

-------------------------------------------------------
Paul Murphy
Head of I.T.
Argenta Discovery
Tel. 01279 645 554
Fax. 01279 645 646