Trouble receiving OTP emails from Microsoft Partner Center

Success!

Jill was able to put me in touch with someone that was able to point me in the right direction. It turns out that Microsoft is sending messages from the microsoft.onmicrosoft.com domain.

From: token(at)microsoft.onmicrosoft.com
Subject: Action required: Please verify your email address

In addition to our organization blocking mail sent from *.onmicrosoft.com domains for security reasons, the messages were apparently being blocked at the M365 perimeter for a period of time because I couldn't even find this in message logs when I first reported the issue back on 1/23/2026.

I didn't see any messages through message tracking in April. However, as of May 28th, they are reaching the message tracking logs!

I suspect the partner center portal was failing to hand the messages off for delivery for a period of time. 

In the meantime:
Dear Microsoft,

Please update the public documentation to reflect that the partner center sends mail from the domain microsoft.onmicrosoft.com, or send the messages from a domain that is already documented. Here's a list of domains Microsoft says are genuine. The implication being that mail from microsoft.onmicrosoft.com is not genuine.

Can I trust email from the Microsoft account team? | Microsoft Support

accountprotection.microsoft.com

How to determine if an email from Microsoft support is genuine - Azure | Microsoft Learn

Microsoft support uses the following domains to send emails:
microsoft.com
microsoftsupport.com
mail.support.microsoft.com
office365support.com
techsupport.microsoft.com

On a side note, I found the following page while looking to see if anyone has encountered this type of issue before and yes, yes they have.

When Blocking onmicrosoft.com Make An Exception For Microsoft – Denny Cherry & Associates Consulting