Learn how external addresses are included to the internal address list by IMSS after migration.
This is not a defect. IMSS extracts all the domains from the "From" field in the route of outgoing policies and the "To" field in the route of incoming policies, assuming that the user defined correct routes for all the policies.
This feature gives the user the convenience of not having to add all the internal addresses one by one after migration. You may delete the external domains from the internal address list manually.