When you remove an alias from the primary domain, users may receive error messages from Google Calendar such as the example below:
“Google Calendar invitations cannot be forwarded via email. This event belongs to user@new.com (the alias domain) and you are logged in as user@old.com (the primary domain). Please ask the meeting organizer to add you to the event from Google Calendar.”
The domain alias provides the users with the ability to accept invitations sent to the alias (new.com) addresses. When this is no longer connected to the primary, users will need to receive calendar invites at their primary (old.com) addresses during the migration. IP address location