Re: AW: Post.Office and spamming

Marc Elbirt ( )
Tue, 18 Feb 1997 12:46:00 -0500

At 08:41 AM 2/18/97 -0600, you wrote:
>There is a simple way to limit these spammers. All of our email boxes are
>limited to 5MB's of email at a time.

This will only help if someone is receiving too much mail, not if an
outside user is sending remote e-mail through your SMTP server.

The only thing that can help, besides changes to Post.Office software, is
to have two SMTP servers. Put one outside a firewall, and the other inside.

The outside one is configured to be able only to send (forward) mail to the
inside one. This way, people can send mail to your users, but messages to
elsewhere will be ignored. The other one is behind a packet filter that
rejects all incoming connections on port 25 (SMTP) except from your outside

You can't have just the inside server, because messages to your domain are
also sent on port 25, and your users would get no mail from the rest of the

But the real solution is for Post.Office to accept messages to be forwarded
only from your domain, but to accept all messages directed to your domain
from anywhere. It is not a monumental fix, but I'm sure it does violate
the RFCs for SMTP. Certainly there are many Unix mail daemons that are
quite capable of this behaviour.

Marc Elbirt Computer Pages Inc.
Systems Administrator 253 Sheppard Ave. West Toronto, Canada M2N 1N2
WWW - Ph: +1 416 225 3030 Fax: +1 416 225 6737