I have some users that were outside of the original scope that need to be migrated from source domain to target domain. These users have a mailbox in the source domain that is not synchronised to the target domain due to unavailable license. I need to migrate the mailbox from the source domain to the target domain but each time the account reverts back.
The steps that I have been taking are:
1. Ensure that the AD sync completed.
2. Set the targetaddress attribute in Active Directory on the source domain to point to the target address for the target domain
3. Remove the targetaddress attribute in the target domain. This address initially pointed back to the source domain.
4. I have exported the emails to pst in the source domain and imported the mail into the target domain
We use extensionattribute11 to sync the user account from the source AD to the target AD. I cannot remove this as the sync is still used for groups, passwords etc.