How does a Collaboration migration handle users that have been deactivated or disabled?
User accounts which have had their Office 365 accounts removed from the Source will not be included in the assessment, nor will they be added as member or owners of the Destination teams. This is true even if the accounts exist on the Destination.
Any chat messages from the removed users will still appear in the Source Teams app until the removals are synced to the Teams database. If the migration happens before the sync, these usernames will still appear in Teams at the Destination, but the accounts will not be active. If the migration happens after the removed accounts are synced, the destination Team will show “Unknown User” IDs on their chat messages.
Blocked (disabled) users are considered valid users during the assessment and are included in the license count. These users will be added as members/owners in the Destination teams.