Mastodawn

To the sysadmin population of the Fediverse: do people have any numbers on how long common mail senders will retry sending mail if your MX is unreachable? Once upon a time people retried for many days, but my impression is that quite a few places now stop trying and bounce the email after quite short intervals, like a day.

(Boosts and practical experiences welcome, like "my MX was down for three days and I still got all that email sent from GMail".)

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Dr. David McBride (dwm)

@cks Will vary depending on temporary vs. permanent failure, but ppsw.cam.ac.uk would keep trying for two weeks, from memory.

(Permanent failures include, "Cannot resolve domain", which can interact excitingly with DNSSEC. So depending on the failure mode, the email might just immediately get returned regardless of retry policies. Also, not all senders send via a proper MTA. :/ Can be particularly problematic with website senders.)