[Mimedefang] Block mail by subject (OT)

[Michael Sims]

WBrown at e1b.org wrote:
> Les Mikesell wrote on 03/24/2004
> 01:17:29 PM:
>> If you reject with an SMTP 5xx, you simply force the previous
>> SMTP relay to do exactly the same thing.  Unless it is the
>> first hop doing the scanning, all you have is the forged
>> header information to construct the error reply, and PC's
>> almost always use a relay.
>
> And it's their own dang fault for passing along spam and/or viruses.
> I refuse to accept responsibility for other's problems.  I certainly
> have (cause?) enough of my own!

I'm curious...What about relays that are doing a ".forward" style redirect?
For example, lets say that one of my mail users registers a vanity domain
and sets up a mail server for this domain and creates an account for
himself.  Let's say that he configures this account to forward to his mail
account at my server using the MTA's ".forward" feature.  Most MTA's default
configurations will accept any email coming to this account, then attempt to
relay it to the address in the ".forward" file.  Now, I can reject with a
5xx during the SMTP dialog all I want, but I am indirectly causing the
vanity domain's mail server to compose bogus bounces to innocent users.  If
this vanity address gets 100 forging viruses in a day, then I am indirectly
responsible for 100 bogus bounces being delivered to innocent users.

Is the vanity domain's mail server at fault in this situation?  Should it's
MTA deliver everything in the foreground, holding open the original SMTP
connection and deferring a final response to it until it sees if my server
will accept the message or not?  (If so, does this approach scale for sites
that accept a large amount of mail?)  Should ".forward" style redirecting be
done away with altogether?

These aren't rhetorical questions...I'm honestly interested in people's
opinions.  It's largely due to the ".forward" factor that I favor
action_discard() wherever possible over action_bounce()...

___________________________________________
Michael Sims
Project Analyst - Information Technology
Crye-Leike Realtors
Office: (901)758-5648  Pager: (901)769-3722
___________________________________________