Re: Reject Unknown Users from SMTP

From: Phillip Helbig (HELBPHI@sysdev.deutsche-boerse.com)
Date: 04/09/03 

From: Phillip Helbig <HELBPHI@sysdev.deutsche-boerse.com>
Date: Wed, 09 Apr 2003 09:53:15 +0100 (MET)

> 50% of all the mail I receive is directed to users at my domain that do
> not exist.

Are the usernames just random, or are they some standard names like
"root" etc?

> This uses up a lot of resources processing the return message, etc.
> Since 99% of it is SPAM, the return message (your message is
> undeliverable) cannot be delivered, so SMTP waits and tries it again up
> to the limit I have set for retries (5). I don't want to change that
> number, since I'd like to continue retrying when required while sending
> out my legitimate mail.

Right. Is the retries value controlled by the same parameter for
incoming and outgoing mail? I've only worried about outgoing stuff.

> Is there any other way to just drop mail addressed to non-existent
> users? I don't even want to TRY to let them know that the user doesn't
> exist. I'm using my SMTP.CONFIG file for other filtering, but I don't
> see a way to do it there.

If most of the stuff consists of a few "standard" usernames (if not, I
can't see the purpose of sending mail, even from a spammer's point of
view), you could (from a suitably priviledged account) do

   MAIL> SET FORWARD/USER=<username> SPAM_TRAP

You could then set up an account SPAM_TRAP and periodically delete the
messages or look for the 1% which isn't spam.

(Note that <username> does not have to exist as an account on the
system, and also that it can be a more or less arbitrary string---in
particular, it doesn't have to be a valid VMS username. You can use
this feature, for example, to make
firstname.lastname@yourdomain.whatever be deliverable to your VMS
machine. You can forward it to a VMS account on your machine or perhaps
to some machine (VMS or not) which your VMS machine can see but the rest
of the world can't (for example, if your VMS mail server delivers mail
for users to their desktop workstation) or of course to any valid
internet email address.)

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