During a ShuttleCloud migration, if a user already has sending from the alias address set up on the source account, that will remain enabled even when the alias domain is removed.
Note: there are two scenarios:
1. Users are already using the destination domain and actively sending from the addresses associated with the address. In this case the send as won’t be affected.
2. Users are not yet actively using the alias domain for email sending and have not set up send as on the source accounts. Removing the alias without having set up send from ability is not problematic because the aliases addresses are not yet in use.