On 2026-02-21 07:49:10 (+0800), Michael Denney via mailop wrote:
I checked mail logs going back to December 2025 - and I see exactly
zero 421 errors. As a matter of fact we have exactly zero 4XX
responses from Outlook - network wide, but I do see 550's with the
error 3150.
Are you sure this is properly implemented?
Feels half-baked as though it was AI vibe coded.
I suspect it's implemented on a network boundary that isn't a sender
boundary. One sender in a /24 is getting the 4xx tempfails and an
unrelated sender in the same /24 gets a 5xx on first interaction.
That's clearly stupid but it's obvious that spam filters are no longer
maintained by sentient humans.
The good (?) news is that there are fewer and fewer humans who care
about email who host theirs at Microsoft.
Philip
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