After a domain is removed / deleted in the source tenant, you migh observe that the accounts' UPN changed and it contains the ObjectID.
Because of this, you might see in ODM that the Source Type is incorrect and Source Email fields are empty in your Accounts project. Because of the incorrect Source Type, the mail migration is blocked, because ODM detects the source accounts as Non-Mail-Enabled Users, instead of Shared Mailboxes or Mail-Enabled Users.
This is a tenant issue, caused by the domain deletion. The way Microsoft removes the domain sometimes leaves accounts in an unexpected state. The root cause of this is not clear.
Update an attribute of a source account, we recommend changing back the UPN to the original value, so that it no longer has the accounts' objectID in it.
After the source UPN has been modified, you should run a Refresh Selected Accounts task in your ODM Accounts project, which will update the Source Type and other fields' values accordignly.
