When attempting to queue a user for migration, the move request failed with the following error in the Windows Event Viewer:
Failed to create new move request for user <username>@<email.domain>.onmicrosoft.com.
Further down in the log is the following message:
Pipeline Errors : 1
Error Record #0:
'The target mail user 'namprd08.prod.outlook.com/Microsoft Exchange Hosted Organizations/<hosted_domain>/<username>' doesn't have an SMTP address that matches the target delivery domain '<domain>.onmicrosoft.com'.'
This may happen if the SMTP address for the user that includes the target delivery domain is not synced to the Office 365 target user.
Once the attributes are set for the user, they may not be possible to change while an active license is applied in Office 365.
To allow the on-premise Exchange server to push the correct attributes, remove the license applied to the user in Office 365.
Then check to see if the correct SMTP target delivery domain address has been applied to the user.
If it still doesn't sync, you may need to manually add it.
Once this is done, you may queue the user for migration again and re-apply the Office 365 license.