No, you'll have to either recreate the user, or provision/deprovision a mailbox. If it's a synced user, adding an 'mail' attribute on-premises should do the trick (well some others might be needed as well, mailnickname/alias for example).
Mail Enable an Existing Azure User
Travis Gallagher
1
Reputation point
Greetings,
I have existing Azure users that I would like to mail enable. I want to be able to add them to a mail enabled security group that I'm using to grant access to an Admin role in our EXO subscription. I can add them to the role, but I'd rather add them to the group so I get the benefit of going to one place to check user access on their account.
Is there anyway to mail enable (not mailbox enable, they don't need a license) an existing user in Azure?
Thank you!