Microsoft is introducing new limits for onmicrosoft.com domains. Organizations can now send a maximum of 100 external emails per day via these standard domains to prevent spam.
The new measure limits messages from onmicrosoft.com domains to 100 external recipients within 24 hours. Previously, there were no limits for Microsoft Online Email Routing Address (MOERA) domains.
Microsoft is responding to an ongoing issue within Microsoft 365. Spammers are abusing new tenants to send large amounts of unwanted emails before Microsoft can intervene. This practice damages the reputation of the shared domain, which affects all legitimate users.
Organizations that exceed the limit will receive Non-Delivery Reports with error code 550 5.7.236. Important to know: internal communication and incoming email remain unaffected by this restriction.
Migration to custom domains necessary
Companies that currently use MOERA domains as their primary domain must take action. Microsoft recommends purchasing custom domains and migrating to them. Only branded domains should still be used for non-test email communication.
The impact extends beyond standard email delivery. Sender Rewriting Scheme configurations, invitations from the Bookings app, and Microsoft product notifications may also be affected if they depend on MOERA domains.
Organizations with federated domains will face additional complexity. They will need to add non-federated custom domains to serve as the default domain.
The 100-recipient limit per day can be restrictive for organizations that regularly communicate externally via their Microsoft 365 environment. This is especially true for companies that have not yet budgeted for their own domain or have not yet taken the technical steps to set it up.
Tip: Microsoft 365 is blocking the FPRPC protocol starting this month