Converting a User Box to a Shared Box in Exchange/Microsoft365.

A shared mailbox ( Shared Mailbox ) in Exchange that is shared by multiple users. Unlike a regular User Mailbox , a shared mailbox account in Active Directory is disabled and cannot be used for interactive logon. This article will walk you through how to convert a regular user mailbox to a shared mailbox in Exchange Server and Microsoft 365.

When converting a user box to a shared one, only the type of the box changes. All existing letters, calendars, permissions to the box and folders in it, as well as the rules in the box remain in place.

• The task of converting a regular box to a shared one usually arises when:You want to share the same mailbox with multiple users, use a shared calendar when scheduling;
• The user leaves the organization and you want to share the contents of the mailbox with the remaining employees. In this case, the user account in AD can be disabled;
• A shared mailbox does not require a separate license.

Converting a mailbox to shared in Exchange Server using PowerShell.

In on-premises Exchange Server 2019/2016/2013, you can convert a custom mailbox to a shared mailbox using the Set-Mailbox PowerShell cmdlet . Use the following syntax:

Set-Mailbox -Identity <MailboxIdentity> -Type <Regular | Room | Equipment | Shared>

Launch a PowerShell console and connect to your Exchange Server. To check the box type, run:

Get-Mailbox -Identity MiriamG| Format-Table Name, RecipientTypeDetails

This is a regular user box (UserMailbox).

To convert this box to a shared one, run the command:

Set-Mailbox MiriamG -Type Shared

The box type has changed to SharedMailbox.

To convert several user mailboxes to shared at once, create a CSV file with a list of users (be sure to include the Email line in the first line of the file) and run the following script:

Import-CSV C:\ps\user_to_shared_mailbox.csv | foreach {Get-Mailbox -Identity $_.Email | Where-Object {$_.RecipientTypeDetails -eq "UserMailbox"} | Set-Mailbox -Type Shared}

Don't delete the user account in AD because the public mailbox is bound to it.

If you need to convert back and make a user box from a public box, run:

Set-Mailbox MiriamG -Type Regular

If you're using an Exchange hybrid configuration, you'll need to migrate your mailbox to on-premises Exchange, convert it, and bring it back to Microsoft 365.

Converting a userbox to a shared one in Exchange Online (Microsoft 365).

In Exchange Online, you can convert a user box to a shared one using the help through the Exchange Admin Center (EAC) or PowerShell.

1. Log in to Exchange admin center;
2. Go to Recipients –> Mailboxes section;
3. Select the user whose mailbox you want to convert;
4. Go to the Others tab and click on Convert to shared mailbox;
5. Confirm mailbox conversion;
6. If the box size is less than 50 GB, you can remove the Microsoft 365/AzureAD license.

The size of a shared box without a license is limited to 50 GB. Check the current size of the Exchange mailbox, and if it is over 50 GB, you need to clean up its contents.

You can also convert a user box using PowerShell. Connect to your Microsoft 365 tenant using the EXOv2 PowerShell module:

Connect-ExchangeOnline

To change the mailbox type to SharedMailbox, run the command:

Set-Mailbox –Identity AlexW -Type Shared

The reverse transformation is performed by analogy:

Set-Mailbox –Identity AlexW -Type Regular

Within 30 days, this box must be assigned a license.