Allow administrators to specify a different domain within which to create group email addresses
Groups are created in our primary domain. That means that users have the ability to reserve email addresses that could be collisions with previous email addresses; current addresses that don't (yet) exist in our Office 365 tenant; and future addresses (unless we remove the address from our assignable name-space).
Even prefix and postfix names provide an opportunity for collision, so it would be much better for us to be able to specify a different domain in which group email addresses will be created.
We believe this is addressed through our recent release of multi-domain support – noted on another ask on this list: https://office365.uservoice.com/forums/286611-office-365-groups/suggestions/9512163-default-domain-name-for-unified-groups.
J. Schlackman commented
The EAP doesn't completely solve the problem because although you can now specify the default domain, the alias of the group in Exchange is global across the entire tenant, preventing the use of that alias in other domains within the same tenant.
A more complete solution could be achieved by assigning Office 365 groups a GUID-like suffix to the alias (and only the alias).
Example: a new group with email address "firstname.lastname@example.org" would automatically be assigned an Exchange alias of "mygroup_22d26ba1", rather than "mygroup" as is the case at present.
In this way, a future group with email "email@example.com", could still be created without collision.
MIEExpert from Belgium commented
Sorry, still not effectively working on our tenant ion Belgium (eiverseau.be)
yes, this is a problem