[Mimedefang] md_check_against_smtp_server and md_graphdefang_log

kd6lvw at yahoo.com kd6lvw at yahoo.com
Tue Mar 26 16:45:31 EDT 2013

--- On Tue, 3/26/13, David F. Skoll <dfs at roaringpenguin.com> wrote:
> Attempting to deliver to nonexistent recipients is by far the most
> common cause of backscatter, and doing an SMTP call-forward on the
> ultimate destination is a simple and cheap way to avoid this.

Point noted, but your response seems to assume (or at least I infer) that no other measures to prevent backscatter are implemented.  At the point that this remote check can be performed, one has already passed the point where an SPF check (and other similar methods) has occurred (or can), and if failed, has probably been rejected during the SMTP transaction thus meaning that this remote check will not be performed.

In my opinion, a message with other than an SPF fail is a candidate for a DSN, although I always reject during the SMTP transaction when possible.  If a domain or hostname manager has not chosen to protect his message source with SPF, that's his problem - because he's effectively saying that he doesn't care about receiving backscatter (or with SPF softfail, wants it), or is too ignorant on how to properly run a mail server and needs a lesson.

I note that DKIM, PGP, and other message validators aren't available at this point.  Those require entering the DATA phase.

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