Jason R. Mastaler <[EMAIL PROTECTED]> writes:
> Ronald Wiplinger <[EMAIL PROTECTED]> writes:
>
> > SMTPRecipientsRefused: {'[EMAIL PROTECTED]': (550, '5.1.1
> > <[EMAIL PROTECTED]>... User unknown')}
>
> This seems to be a Sendmail-ism, I've seen similar reports before.
I'm not sure this is entirely sendmail specific. What I would guess
happened is that Ronald received a spam where the envelope sender was
set to a random address in Ronald's domain.
TMDA attempted to send a confirmation request via SMTP, but the local
MTA rejected the transaction because the recipient is undeliverable.
TMDA logs debug messages when the SMTP transaction fails, and returns
a soft error to the MTA. This means that the offending incoming
message sits in the MTA queue for a while, and eventually times out
(with an undeliverable bounce that will go to sendmail's double-bounce
address, postmaster by default).
This isn't a major problem (and you can switch off the sendmail double
bounce feature to prevent postmaster receiving the bounce), but it
does mean that you'll never see the message in your TMDA pending
queue.
IMHO, TMDA should just silently errors such as 550 when sending
confirmation requests. It is no different from the more common
situation with a bogus return address, it's just that usually the mail
makes it out of your site, and is then dropped by the destination MTA
as undeliverable. (Note, dropped, not bounced, because the envelope
sender is <>.)
-roy
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