Subject: Re: Last Call: Anti-Spam Requirements on an SMTP MTA to BCP

From: Gunnar Lindberg <[email-masked]>
Date: Tue, 3 Mar 1998 17:48:03 +0100 (MET)

>Date: Mon, 2 Mar 1998 12:48:14 +0000
>From: Richard Clayton <[email-masked]>
> ...

The first part of the mail has already been discussed and I assume
there is more to come. It would be nice to get <[email-masked]>
on the Cc: list (I forgot in my prevoius reply).

>Refusing to accept mail because the senders DNS is wrong or
>inconsistent
>is completely at odds with the Fundamental Principle of being
>liberal in
>what one accepts.

You may actually view if differently: If you accept mail whose
"MAIL From:" does not resolve in the DNS, you actually take on
a responsibility to manually trace the sender in case "RCPT To:"
is non-existent or fails by any other reason. This is especially
important if you've accepted to be a Relay (secondary MX etc).

If the response is "4xx" you actually leave that problem to the
sending host - you don't even touch mail that you cannot Error
Return. In the long run this kind of "pushes back" nearer to the
(incorrect) sources.

Liberal? Nope. Strict? Yes. Anti-spam? Probably. Careful?
Yes, I honestly think so. Correct? Well, *I* think so...

>As I understand the current state of deliberations, 551 is being
>explicitly deprecated by DRUMS. I expect this should be 550
>throughout.

I assume this is from draft-ietf-drums-smtpupd-06.txt. Now using
a value from one draft in another draft is risky, but "550" is
"equally much 5xx" for this, so I'll be happy to change.

>From: Owain Vaughan <[email-masked]>

>Plus it says RCTP To: rather than RCPT To:

Thanks for catching that typo!

	Gunnar