On 06/06/2020 19:40, Stefan Bauer via mailop wrote:
keeping rejected mails in queue for second attempt acceptable?
Hi,
once in a while, some of our outgoing customer mails are rejected by
remote sites with a 500 code because one of our sending IPs are
temporary blacklisted. or due to other reasons we are not able to
deliver the mail. I'm only talking about cases, where the mail itself,
is not the reject reason.
Well, if the sender has been temporarily blacklisted, they shouldn't get
a 5xx error - the clue is in the "temporarily". That's what the 4xx
response codes are for.
Strictly speaking, you shouldn't retry a 5xx-rejected message exactly as
it was sent the first time, but no one can stop you from doing so.
You can't be certain whether a message was rejected due to the message
or due to a temporary problem unless you know exact responses that
you're getting, and can check for those. That's why the receiving MTA
should return a 4xx for a temporary problem.
--
Paul
--
Paul Smith Computer Services
Tel: 01484 855800
Vat No: GB 685 6987 53
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