"Active Directory property ‎'homeMDB‎' isn't writeable on recipient" error when moving a mailbox to Microsoft 365

Symptoms

When you move an on-premises Exchange mailbox to Microsoft 365, you receive the following error message:

Error: MigrationPermanentException: Active Directory property ‎'homeMDB‎' isn't writeable on recipient ‎contoso.com/Users/mailbox. --> Active Directory property ‎'homeMDB‎' is not writeable on recipient ‎contoso.com/Users/mailbox‎‎.

Cause

This issue occurs for either or both of the following reasons:

• The Include Inheritable permission from this object's parent/Enable Inheritance check box is not selected.
• The on-premises server that's running Microsoft Exchange Server that's used from proxy isn't a member of the Exchange Servers and Exchange Trusted Sub Systems role groups.

Resolution

To resolve this problem, follow these steps:

1. Make sure that the Include Inheritable permission from this object's parent/Enable Inheritance check box is selected in the <User Account> Properties dialog box of Active Directory. To do this, follow these steps:

   1. Open Active Directory Users and Computers, select View, and then select the Advanced Features option.
   2. Open Active Directory Users and Computers, locate the affected user, select <User Account> Properties, select Security, and then select Advanced.
   3. Select the Include Inheritable permission from this object's parent/Enable Inheritance check box.

2. Make sure that all servers that are running Exchange Server in the organization are the members of the Exchange Servers and Exchange Trusted Sub Systems role groups. To check or add members, follow these steps:

   1. Open Active Directory Users and Computers.
   2. Select Microsoft Exchange Security Groups.
   3. Select Exchange Servers/Exchange Trusted Sub Systems, select Properties, and then select Members.
   4. Select Add.