Consider, on the source domain there is a group named firstname.lastname@example.org having 6 members in it.
Source Group : email@example.com
Out of the 6 users 4 are from the source domain vopak.com & 2 are from an external domain. Out of the 4 VoPak users, only 2 users are in the migration list
( firstname.lastname@example.org => email@example.com),
( firstname.lastname@example.org => email@example.com ).
Now, when we migrate the group, a group named firstname.lastname@example.org will be created at the destination domain with the following users.
Destination Group : email@example.com
As you can see above, the users who are migrating have been mapped correctly into the group. The non-migrating users have just their domain replaced with their usernames. The external domain users are retained as same.
Case 1: What if a group named firstname.lastname@example.org is already present with some users are present in the group?
Answer: The groups will be merged, the users will be merged into it.
Case 2: What if the email email@example.com of the group is already assigned to a user at the destination?
Answer: In this case, we can't migrate the group. Because, when trying to migrate the group firstname.lastname@example.org, we try to create a group email@example.com at the destination. Then, Google will provide a error that we can't create a group with that name since it has been already taken by a user in the destination domain.