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How to Fix Accepted Domain Error During Cross-Tenant Email Migration
Question details
Users need to resolve an Exchange migration error stating that an onmicrosoft.com domain is not an accepted domain.
- Product
- Microsoft Exchange Online
- Device & OS
- not provided
- Scenario
- Migrating emails across Microsoft 365 tenants using Exchange Online.
- Observed behavior
- The migration fails because the source or target organization does not recognize the specified onmicrosoft.com domain in its Exchange Online configuration.
Ensure you have Global Administrator or Exchange Administrator privileges in both the source and target Microsoft 365 tenants to view and modify domain configurations.
Verify Accepted Domains and Migration Endpoints
Check and correct the accepted domain configurations and organization relationships in the Exchange Admin Center.
This error typically occurs when the routing domain (e.g., tenant.mail.onmicrosoft.com) is missing or misconfigured in either the source or target tenant's accepted domains list.
Log in to the Microsoft 365 admin center with your administrator credentials and navigate to the Exchange admin center.
Go to Mail flow > Accepted domains. Verify that the required onmicrosoft.com routing domain is listed and configured properly for the tenant.
Navigate to Organization > Sharing to ensure the organization relationship between the source and target tenants is established and recognizes the correct domains.
After confirming the domain configurations, open Exchange Online PowerShell and run the Test-MigrationServerAvailability cmdlet to validate the connection.
Open a Microsoft 365 Support Ticket
If domain settings are correct but the migration still fails, contact Microsoft Support for backend assistance.
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Frequently Asked Questions
What does the 'not an accepted domain' error mean in Exchange?
This error means that the target or source Exchange Online environment does not have the specified routing domain (typically an onmicrosoft.com domain) registered or configured as an accepted domain for mail flow, preventing the migration from proceeding.
How do I check my accepted domains in Microsoft 365?
You can view your accepted domains by logging into the Exchange admin center, expanding the 'Mail flow' menu on the left sidebar, and clicking on 'Accepted domains'.
Why is my onmicrosoft.com domain missing from accepted domains?
In some cross-tenant scenarios, backend synchronization delays or provisioning errors can cause the default routing domains (like tenant.mail.onmicrosoft.com) to be missing or unrecognized. Re-verifying the domain or contacting Microsoft support usually resolves this.
