Does everyone in a Group need to have the same email?

No.

But if you are a Retainer client with unlimited access you will have a code that allows you to add users to a new Group at no cost. This is useful if you need to form a new Group for a new production, for example, rather than just add users to an existing one.

In order to set up a new Group at no cost, the code to do so is limited to authorised email addresses / domains only for obvious reasons – or anyone could benefit from your account terms.

So the email restriction only applies to who can set up a Group and benefit from the unlimited access enjoyed by some retainer clients, not to who can be added to that Group.

So, once the Group is set up (by an authorised user) there are no restrictions on who you can add to the Group. You just need a valid email address for each person, plus a first name and last name. They can be added by any Group Leader you have nominated in the usual way.