Limiting Onmicrosoft Domain Usage for Sending Emails

Posted on by Lobsang Wangmo

April 28, 2026

Lobsang Wangmo

Microsoft 365 Announcements

Date: April 28, 2026
To: ACE-IT, MTRC, EITU, InfoTech Listserv, Tri-campus Help Desk Leads  
From: Enterprise Applications & Solutions Integration 
Re: Limiting Onmicrosoft Domain Usage for Sending Emails

 

Dear colleagues, 

Microsoft has announced a policy change affecting email sent from default onmicrosoft.com domains, also known as Microsoft Online Email Routing Address (MOERA) domains. This update is intended to improve email deliverability and reduce misuse across shared Microsoft-managed domains. 

What is changing 

Microsoft has stated that MOERA domains should no longer be used for regular outbound email. As part of our internal review, we have identified a number of system-generated mailboxes (such as Microsoft Bookings mailboxes) that currently use the onmicrosoft.com domain for sending email. We are making configuration updates to ensure these services use the institutional domain for outbound email. 

Who is affected 

This change will affect: 

    • Using an onmicrosoft.com domain as the primary SMTP address for mailboxes.  
    • Applications, scripts, or devices that send email using onmicrosoft.com addresses. 
    • Services configured to send notifications or invitations from MOERA domains. 
    • Hybrid environments or workflows where onmicrosoft.com domains are used as fallback or default sender addresses. 

Before and during the configuration update, we will be sending targeted communications to the following groups: 

    • Departmental local IT teams for Outlook Shared Resource Calendars, Mail-enabled Security Groups, etc. 
    • Owners of Microsoft Bookings pages (excluding Bookings with Me) 

For other account types, including Teams Spaces, Distribution Lists, and Microsoft 365 Groups, no user impact is expected. If you experience any issues sending emails for these account types, please open a support ticket (https://uoft.me/m365help). 

Timeline 

    • For our tenant, this change will begin rolling out on June 1, 2026.  

Learn more: Limiting Onmicrosoft Domain Usage for Sending Emails 

If you have any further questions or concerns, please submit a ticket to the Enterprise Service Centre at (https://uoft.me/m365help). 

Kind regards, 

Enterprise Applications & Solutions Integration (EASI)
Information Technology Services, University of Toronto