According to Microsoft:
A shared mailbox is a mailbox that multiple users can open to read and send e-mail messages. Shared mailboxes allow a group of users to view and send e-mail from a common mailbox. They also allow users to share a common calendar, so they can schedule and view vacation time or work shift.
There is no direct way to convert a Shared Mailbox (SM) to a normal user mailbox (Regular Mailbox – RM), through Office 365 settings.
So, in order to convert a SM to a RM, we must use PowerShell, with a very simple cmdlet.
Log In to Admin using PS
Use the following PS script to log in:
# 1.Ask for credentials:
$LiveCred = Get-Credential
# 2.Create a new session:
$Alex = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://ps.outlook.com/powershell/ -Credential $LiveCred -Authentication Basic -AllowRedirection
# 3.Join the opened session:
From the Admin section click on the Admin menu and choose Exchange, to access the Exchange Control Panel.
From the Recipients section click on Shared.
As we can see, there is just only one SM, with the display name: Office
Use a cmdlet
To convert it, we must use the Set-Mailbox cmdlet.
The entire cmdlet is: Set-Mailbox „Office” – Type:Regular
After the conversion, the SM will be converted into a RM.
As an personal observation, I’ve noticed that if you do this operation more than twice, you will receive an error saying that the object (SM display name) doesn’t exist.
After five minutes, I was able to convert another two SM.