Reuse/convert a Shared Mailbox alias to a alias of an active user?

Occasional Contributor

3 Questions

  • What I found so fare. I can give the shared mailbox a new alias, delete the active user that was auto-created when the shared mailbox was initially created, then wait for ~15min, and then add the old alias that i just deleted to the active user as an alias.
  • Creating a new shared mailbox also creates an active user with the same mail, why?
  • Convert a shared mailbox into an alias for existing user, how/the right way?

Why I need to do this:

I have a client (accountant) that have created 20+ Shared Mailboxes for her own clients, so that a client would send their invoices, hours etc. to a mail like: clientcompanyname(at) They then pick up thier mails and do their thing. - Downside to this is Outlook really hates this many shared mailboxes.

So what i want to do is setup a single bookkeeping(at) mail for my client convert/reuse the shared mailboxes aliases as aliases for bookkeeping(at) and then create rules to add incomming mails to the aliases to different subfolders. - This works great, as far as I have tested.

Problem, converting the shared mailboxes into alias addresses of the new bookkeeping(at), is a hassel.

Second, also I do NOT want to delete a share mailbox, with mails in.

Third, as stated in the begining, what is the point of O365 creating an unlicensed user when i add a shared mailbox?


Looong post, sorry. :) 

12 Replies

Every mailbox in Exchange comes with a corresponding user object, shared mailboxes included. The only difference is that for shared mailboxes this is a "managed" user account, for which you generally shouldn't care about.


Anyway, for your scenario simply add a new alias to the shared mailbox and remove the one you want to re-use. Do not delete the user object. After a min or so you should be able to assign the alias to another object.

I have tried what you suggested. Adding a new alias to the shared mailbox, set ithe new alias as primary and deleting the old one.

But instead of being able to reuse the alias, after 1min it just pops right back up as a secondary alias for the shared mailbox. And of course I am then unable to reuse it. 

This is due to the alias / mailnickname field of the shared mailbox not being changed and you are just editing the e-mail addresses manually. There typically is a default mail policy that creates the primary e-mail address off this mailnickname attribute. Wouldn't you just keep the aliases all on the single mailbox and keep your rules there to route the messages to the folders? Moving the alias away seems to be a hassle.

Anyway, if you have to move it, set your actual alias (Below Display name in EAC) on the shared mailbox first, to the new name and this will generate a new primary e-mail address. Then wait and you can remove the "e-mail address" and assign it to another user/shared mailbox.

Um, there are no email address policies in O365. Most likely the OP is trying to make the change from the O365 admin center... which is known to cause more harm than good with its "helpful" "features". I'd suggest making the change via PowerShell or the EAC.

Aaaaand I just remembered that we do need to have at least one alias matching the UPN. Wonder why I blog about things, just to forget them later:

Oh is there not? I've always sat on Hybrid that still had address policies just assumed it would default as well in 365. My bad ;).

If you are on hybrid thegreatdane, then it could be the policy issue I talk about in my response, otherwise prolly not :P. If you could give a few more specifics to how you are trying to make the change and environment we can go from there.

Well there is, but it only applies to Groups. And we also have the "feature" that enforces at least one alias to match the UPN, which kinda works like an EAP.

Interesting. So it still sort of has an address policy :P. Good read.

Hey Chris


I'm on a pure cloud solution, and just starting out so all this policies/powershell is still new to me. But im getting there :)

Hey @Vasil Michev 


Thanks for the post, thats seems spot on. Did I understand it correctly, that you are unable to control/change which alias matches the UPN? And therefore are unable to delete/reuse it?


Also thanks @Chris Webb for your comments, it all helps to get me going.



Hmm if I rename the alias of the user object linked to the shared mailbox, it seems to work. Also that would be okay, since the shared mailboxes are going to be deleted later on.


Although i don not know if this is a bad way to do it and a noobish attempt to work with O365. I am still trying to figure out what is best practices vs idiot fumbling (me). :)  

best response confirmed by thegreatdane (Occasional Contributor)

Can be either secondary or primary, but in any case you can just change the UPN to anything you'd like and "free" the alias.