getting issue while migrating mail through microsoft exchange native tool

Question

The migration service is trying to access the destination mailbox, but Exchange Online cannot find the mailbox object on the backend server, even the user exist in admin center with standard license. how to resolve it

[Moderator note: Personally Identifiable Information removed]

Answer 1

Dear @Megha Devrani,

I understand you are encountering the MigrationProvisioningPermanentException error where Exchange Online states the object/mailbox cannot be found on the backend server, even though the user exists in the Admin Center with a license.

This error typically occurs during native migrations (such as Google Workspace or Staged/Cutover migrations) due to one of three main reasons:

Step 1: Recipient Object Type Mismatch (Most Common)

Native migration batches often require target users to exist as Mail Users (MailUser) initially so Exchange Online can establish the target environment before provision/cutover. If a user is already assigned an Exchange Online license, Microsoft 365 provisions them as a User Mailbox (UserMailbox). The migration service then fails because it looks for a MailUser object and cannot locate it on the server.

• How to check: Connect to Exchange Online PowerShell and run:

Connect-ExchangeOnline

• Run the following command in your PowerShell window:

Get-ExoRecipient -Identity ******@yourdomain.com | Select-Object DisplayName, RecipientType, RecipientTypeDetails

• If the RecipientType is UserMailbox, temporarily remove the Exchange Online license from the user account to revert/clear the mailbox state (or delete/re-create the object as a Mail User), start/complete the migration batch, and then re-assign the license afterward.

Step 2: Delay in Backend Provisioning / Directory Sync

Even if a license is assigned, directory sync between Microsoft Entra ID (Azure AD) and Exchange Online backend databases can occasionally take time.

• Unassign and re-assign the Exchange Online license in the M365 Admin Center to force a re-provisioning trigger.
• Wait approximately 15–30 minutes for backend replication to finish.
• Verify that the user can access Outlook on the Web (OWA) directly before re-initiating the migration.

Step 3: CSV Identity / Domain Mismatch

If you are using a CSV file to map target users, the primary SMTP address or User Principal Name (UPN) specified in the CSV might not match the primary address provisioned in Exchange Online.

• Verify that the email address in your migration CSV strictly matches the user's UserPrincipalName and primary SMTP address listed in Exchange Online.

For step-by-step guidance on managing mailbox migration types, you can refer to the official Ways to migrate multiple email accounts to Microsoft 365 or Office 365 | Microsoft Learn

Please let me know if checking the RecipientType via PowerShell helps resolve the issue.

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