MOERA domains for email
When a organization creates a new tenant in Microsoft 365, an onmicrosoft.com domain (or similar default domain like onmicrosoft.de) is provided. These MOERA (Microsoft Onli...
Updated Mar 30, 2026
Version 9.0
Blog Post
Hi The_Exchange_Team ,
I’m looking for clarification on the upcoming MOERA (*.onmicrosoft.com) domain throttling enforcement.
Based on the announcement, my understanding is that throttling decisions are made using the P1 (SMTP envelope / MAIL FROM) address, rather than the visible From header.
Scenario:
- Microsoft Bookings emails present a MOERA address in the From header
- The P1 / Return-Path is set to a custom domain (not onmicrosoft.com)
Question:
In this configuration, will these messages be subject to MOERA throttling, or is enforcement strictly based on the P1 address (i.e., only messages with onmicrosoft.com in P1 are throttled)?
Thanks in advance for your clarification.
SeanMSFT
Microsoft
MicrosoftNo. If the P1 Mail From is your custom domain, the throttling rolling out will not affect it. It would still be good to follow the steps to Bookings to stop using MOERA domains altogether though.
Thanks for clarifying. We’ve followed the steps provided to ensure that all newly created Booking pages now use the custom domain.
This question is specifically about existing Booking pages that were originally created using the MOERA domain.
To transition those older Booking pages without having to recreate thousands of them across our institution, we updated each page so that the PrimarySmtpAddress now uses the custom domain. However, the visible sender (P2 From address) still defaults to the MOERA domain. This happens because the MOERA domain remains on the mailbox as an alias to ensure the original Booking page URLs continue to function as these URLs have been published and used widely for years.
The P1 (envelope MAIL FROM) correctly reflects the custom domain, but the P2 visible From continues to show the MOERA domain.
This helps confirm that we can transition the older Booking pages away from the MOERA domain transparently, without impacting the end‑user experience.