Creation of shared mailbox failed saying "email address already being used" but this is the only Exchange server for the domain

Question

I recently moved a domain from SimpleLogin to Exchange, and I want to create a shared mailbox for ******@moveddomain.com, but I get an error message saying the email address is already in use so Exchange can't create a shared mailbox.

It is true that in SimpleLogin there was an email ******@moveddomain.com, but I deleted that about a week ago just in case that was messing things up.
I tried doing the "Get-Recipient" powershell command and it came up empty.

So I'm stuck. Anyone with any ideas on what needs to be cleaned up?

Answer 1

Hi @Wildcat63

Based on your description, do you mean that the same alias is used in different domains?
If so, the error message is expected behavior, because the alias must be unique within the organization.

We recommend that you use different aliases and display names to create shared mailboxes.

Additionally, if you must want to use the same alias in different domains, you can refer to the document. create-shared-mailbox-same-alias (Note: The environment is Microsoft 365)
Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

---

If an Answer is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

I was unaware of this but if you want ******@domain1.com and ******@domain2.com, you will need a unique alias for each in order to create both shared mailboxes. Otherwise you will get the error mentioned in the title to the question.