Hi !!
>> How many MTAs accept a 551 redirect when they are sending mail on to
>> another MTA?
>> Of those that don't, what happens? Dropped mail, bounced?
>
> Exim bounces. It does not distinguish between 5xx responses.
If no MTA supports it and giving 551 codes will end in lossing mail
which is the purpose of implementing it ? If exim implements 551
codes it must implement both parts (client/server) and must have a
way to recognize if remote client supports it or not (via some
propietary EHLO extension)
and what about using RFC 1035 experimental 'MR' (Mail Rename) 'MB'
(Mailbox) and 'MG' (Mail Group) DNS records ?
--
Best regards ...
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