i am trying to convert an Office 365 Group into regular shared mailbox. I know there is no simple way to do that. I have a group with email address it @domain.com, I have change this address from Microsoft 365 admin center to it_group @domain.com, I also removed the old email address from aliases but I still cant use this address as address for new shared mailbox. In Exchange Online PowerShell when I use:
Something fishy is happening here, I tried playing with the aliases for one of my group and few minutes later, the original set of alias was restored. I'll try poking around more, in the meantime I'd suggest you open a support case.