Le 29/06/2026 à 09:11, Viktor Dukhovni via mailop a écrit :
On Mon, Jun 29, 2026 at 08:25:43AM +0200, Tobi via mailop wrote:
in the last days we're seeing that Microsoft is using
"forms.mail.microsoft" as envelope SMTP sender-domain. As this domain
does neither have A or MX it's considered unresolvable by our postfix
MTA. Anyone else seeing that domain in their mailflow?
Perhaps the MX RRset is newer than the messaegs you recorded, or perhaps
there's a DNS issue on your end.
Another possibility
Toby, are you on an IPv6 only network ?
I can see on Zonemaster that Microsoft's NS for `mail.microsoft.` does
not respond to IPv6 queries
https://zonemaster.net/en/result/3942ad544f4c9a1e/
Same goes for `cloud.microsoft.`
https://zonemaster.net/en/result/f97b652ebbe9fb52/
--
Grégory Rocher
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