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Re: [ietf-smtp] SMTP Greylisting Retry Hints + PRDR

2019-02-08 11:59:03
Hi John,
At 07:21 AM 08-02-2019, John R Levine wrote:
How reliably does that work? If I were writing an MTA I'd think a mix of 2xx and 5xx is likely but 2xx and 4xx is unexpected.

Both the 4xx and 5xx can occur. The latter might be for a "mailbox not found" reply code. The receiver might not want the sending MTA to retry in such a case. The mix usually works.

S. Moonesamy
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