On 2020-12-15 18:04, Chris Wedgwood via mailop wrote:
things break, it happens...
but why 5xx (vs 4xx) in this case?
this means means emails are being lost, some of won't/can't be resent
and recovered
with 4xx most of them would be delivered once things come right
the confidence in a hard-bounce in this instance seems misplaced
Well, yes. But receivers get <bleep bleep bleep> pissed off if you
continuously ignore 5xx "just because I can't trust them". I've been
known to firewall such abusers regardless of whether their email is
spam/abusive. The retries are THEMSELVES are abusive.
You don't want receivers <bleep bleep bleep> pissed off at you. You
really don't even want large receivers to NOTICE you. If they're forced
to notice you, you lose.
The mailing industry has come up with fairly reasonable compromises.
Including exponential backoff, a heavily limited number of retries, or
my favourite: simply taking them at face value, but you don't have to
remove the recipient from the original list until a threshold number of
consequtive 5xxs occur over a reasonably long period of time with
different emails.
I don't know the precise details of, say, the M3AAWG senders WG's
working papers recommend as BCP. But say, 5 5xxs from 5 different
emails over a week or more, sounds like a good starting point for list
removal.
Yes, some email will get lost. Personal high-importance email will get
through anyway (perhaps over the phone or whatever). But it's still
better than being firewalled.
_______________________________________________
mailop mailing list
[email protected]
https://list.mailop.org/listinfo/mailop
