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bug#34177: smtpmail.el aborts on transient errors
From: |
Lars Ingebrigtsen |
Subject: |
bug#34177: smtpmail.el aborts on transient errors |
Date: |
Tue, 09 Jul 2019 20:24:19 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) |
Brian Sniffen <bts@evenmere.org> writes:
> smtpmail.el treats all return codes over 400 as errors, and aborts.
> But RFC 821 and successors call the 400-series “transient” errors and
> suggest retrying immediately. Some mail servers, including current MS
> Exchange, use 400-series errors for load limiting. The user can just
> repeat C-c C-c until the mail goes through... or Emacs SMTPmail could
> loop until the server accepts it.
>
> Retrying is a little tricky in the case of multipart commands like
> LOGIN, but in general it’s safe to loop for seconds on any command.
This is what RFC 5321 says:
https://tools.ietf.org/html/rfc5321#section-4.2.1
4yz Transient Negative Completion reply
The command was not accepted, and the requested action did not
occur. However, the error condition is temporary, and the action
may be requested again. The sender should return to the beginning
of the command sequence (if any). It is difficult to assign a
meaning to "transient" when two different sites (receiver- and
sender-SMTP agents) must agree on the interpretation. Each reply
in this category might have a different time value, but the SMTP
client SHOULD try again. A rule of thumb to determine whether a
reply fits into the 4yz or the 5yz category (see below) is that
replies are 4yz if they can be successful if repeated without any
change in command form or in properties of the sender or receiver
(that is, the command is repeated identically and the receiver
does not put up a new implementation).
So, indeed, smtpmail SHOULD try resending when given a 4xx response
code... but presumably not forever, either.
It's a bit difficult to test, though. Does the following patch work for
you?
--
(domestic pets only, the antidote for overdose, milk.)
bloggy blog: http://lars.ingebrigtsen.no
retry.patch
Description: Text Data
- bug#34177: smtpmail.el aborts on transient errors,
Lars Ingebrigtsen <=