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Re: [ietf-smtp] Obsoleting RFC5321 552 -> 452 workaround

2019-12-19 05:21:59
On 19/12/2019 10:58, Jeremy Harris wrote:
On 19/12/2019 09:46, Peter J. Holzer wrote:
I vaguely remember that there was a draft for an extension where the
server could communicate  a hold time to the client. Something like "try
again in 5 seconds" for too many recpients or "try again in 24 hours"
for a full mailbox.
There was
but I don't think it gained traction.

That is actually mildly widely used. There are MTA clients which look for hints in a 4xx response to decide when to retry and the 'retry=hh:mm:ss' text is one of the hints they look for.

It's a trivial-effort thing for a server to implement, and not-much-more-effort thing for a client to implement if it can already handle different per-message retry delays.

But it was designed to 'optimise' greylisting, so may not be useful for this scenario (but it may be - after all, the client can't always work out WHY the message was temp rejected).


Paul Smith Computer Services
Tel: 01484 855800
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