On 18/06/2025 09:49, Benny Pedersen via mailop wrote:
Muthulakshmanan, Thiyagarajan skrev den 2025-06-18 10:39:
Mostly sounds like Microsoft rolled out some change during that time
and did not implement DKIM fail or DMARC align check properly.
microsoft should not reject based on spf, dkim
this is a job for dmarc only
Microsoft have decided, in their wisdom, that large senders to them have
to match DKIM *and* SPF *and* DMARC.
As long as lots of people choose to use Microsoft for their email,
everyone else will have to meet their arbitrary terms.
https://support.microsoft.com/en-gb/topic/fix-ndr-error-550-5-7-515-in-outlook-com-34cfe8f8-6fbf-457e-9e8b-9e4dbaf4e0ef
"What defines a high volume (large) sender?
====================================
You send 5,000 or more email messages to Microsoft consumer email services.
(((it's uncertain over what time period this 5000 message limit applies)))
and
All of the messages use the same domain in the 5322.From address.
After you reach this threshold, we expect all messages from senders in
the domain to meet all of the following email authentication requirements:
Publish SPF and DKIM records for the domain: ***Both SPF and DKIM checks
must pass***
Publish a DMARC record for the domain: For example:
Hostname: _dmarc
TXT value: v=DMARC1; p=none
***Messages from senders in the domain must pass DMARC validation***:
The SPF and/or DKIM record (at least one) must align with (effectively,
"include" or "match") the domain in the 5322.From address."
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