Re: SMTP server error message

[Achim Gratz]

Eli Zaretskii writes:
> Since about a couple of days ago, some of the messages I send via
> smtpmail fail because the SMTP server sends this response, after the
> message is sent to it:
>
>   451 4.0.0 Spam filter end message failed - server - license [slot 1]

The 451 repsonse means there has been an error on the server while
processing the message and the pending action has been aborted.

> When this response comes in, smtpmail bails out.  This only happens
> with about 25% probability, and in particular if I immediately resend,
> the message is sent with no problems.

You might be talking to an address that uses load-balancing over
multiple servers and only one of those has a problem.  Another
possibility is that whatever is doing the spam filtering doesn't respond
(quickly enough).

> What does that response mean, and what can I do to avoid it (apart of
> hacking smtpmail)?

Getting a 451 means, "Sorry, didn't work out this time.  Come back later
if you still want to."  Most SMTP servers would now enter exponential
backoff for re-delivery attempts, most MTA will simply bow out and let
the user handle the problem.


Regards,
Achim.
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