Making a mailbox shared

When working with SMB customers without a clear IT strategy on how to store communication data between customers, you, at least I, get this question allot.


Alex Darrow, who works as a project manager, quit!

He have removed all personal email from his mailbox, and now we want to give Anne Wallace and Sara Davis access to his mailbox.

Can you fix?

Of course I can! What I will do is to convert his mailbox into a shared mailbox, and grant the two users access to it. My first tool will be PowerShell.

Sing in to Exchange Online using PowerShell

$UserCredential = Get-Credential

$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri -Credential $UserCredential -Authentication Basic -AllowRedirection

Import-PSSession $Session

Then some magic. With the Set-Mailbox command, I’m converting this mailbox into a shared one

Get-Mailbox -Identity "Alex Darrow " | Set-Mailbox -Type Shared

This task could take some seconds/minutes, so just be patient.

Then I sign in Exchange Admin Center, and check that the account shows under Shared. The great thing about shared mailboxes is that they do not need an Exchange Online license.

Therefore, I sign to Office 365 admin center and remove the license from the user.


When I click save, and then confirm with Yes, I get a warning saying that all data will be removed.


I have still not experienced that a regular mailbox that has been converted to a shared mailbox loses any data when the license is removed, so I click Yes.

Now I rename the account from within Office 365 admin center. This is not required, but it makes management easier later on when accounts have a logical name. I usually append “- Shared” in the Display Name, and just “Shared” in the user name. It’s short and logical.


Then, as a final step, I assign the access rights for the mailbox. I do this via PowerShell, but I could have done just as easy from Exchange Admin Center

Get-Mailbox -Identity "Alex Darrow - Shared" | Add-MailboxPermission -User "Anne Wallace" -AccessRights FullAccess -InheritanceType All

Get-Mailbox -Identity "Alex Darrow - Shared" | Add-MailboxPermission -User "Sara Davis" -AccessRights FullAccess -InheritanceType All

Then ask one of the users to try opening the mailbox. If they use Outlook Web App, they have to manually Open another mailbox



If they are using Office 365 ProPlus, the mailbox is automatically opened next time Outlook starts.

A few notes

The Exchange Online Limits document in the Office 365 Service Description states that a Shared Mailbox only have 10GB of storage, and that it required a license to use futures like Online Archive. However, when you create a new Shared Mailbox, it’s ProhibitSendReceiveQuota is set to 50GB. Therefore, remember to configure this, so you don’t get unexpected NDR reports down the road.

Remember to remove the SMTP address from the mailbox, unless you want to risk getting personal mail addressed to Alex.

One final thing, which is a tip many should use more often. Always make sure to have a copy of important data before changing stuff in a production environment. Although, in this case Microsoft would be able to restore your data if you should loose anything, by making a Service Request, it gives a extra good feeling knowing that: If I screw up this, I will be able to fix it 🙂

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