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Subject: Re: reject_unknown_sender_domain - still relevant?
From: Greg A. Woods (woodsmost.weird.com)
Date: Sun Feb 06 2000 - 10:58:37 CST

[ On Sunday, February 6, 2000 at 09:04:51 (-0500), Wietse Venema wrote: ]
> Subject: Re: reject_unknown_sender_domain - still relevant?
>
> Miguel A.L. Paraz:
> >
> > I note that the vast majority of "Domain not found:" messages due to
> > 'reject_unknown_sender_domain' are from misconfigured sender mail systems, or
> > misspellings in user MTA's.
>
> In my case, it is effective and catches a lot of bogus mail.

Indeed! ;-)

Ideally all properly configured MTAs acting as gateways, especially
those for simple-minded MUAs that use SMTP for delivery will verify not
only that the domain in the SMTP envelope from address is valid, but
also that the mailbox portion is valid if it would be delivered locally
too. Such MUAs are extremely easy to mis-configure (or rather
impossible to knowingly configure correctly without external
verification) and many users don't understand the consequences of not
getting their sender address right. On even small ISPs I've seen
hundreds of bounces that could not be returned to my local users because
they had not set their mailbox correctly. Since adding mailbox
validation for local sender domains these undeliverable bounces have
almost completely disappeared (now all that remain are those that fail
due to over-quota mailboxes). 

-- 
							Greg A. Woods

+1 416 218-0098      VE3TCP      <gwoodsacm.org>      <robohack!woods>
Planix, Inc. <woodsplanix.com>; Secrets of the Weird <woodsweird.com>