Convert a user mailbox to a shared mailbox

When you convert a user's mailbox to a shared mailbox, all of the existing email and calendar is retained. Only now it's in a shared mailbox where several people will be able to access it instead of one person. At a later date, you can convert a shared mailbox back to a user (private) mailbox.

Before you begin

Here are some really important things that you need to know:

  • The user mailbox you're converting needs a license assigned to it before you convert it to a shared mailbox. Otherwise, you won't see the option to convert the mailbox. If you've removed the license, add it back so you can convert the mailbox. After converting the mailbox to a shared one, you can remove the license from the user's account.

  • Shared mailboxes can have up to 50 GB of data without a license assigned to them. To hold more data than that, you need a license assigned to it. You may need to delete a bunch of large emails (say, ones with attachments) from the shared mailbox to shrink it down so you can remove the license.

  • Don't delete the old user's account. That's required to anchor the shared mailbox. If you've already deleted the user account, see Convert the mailbox of a deleted user.

  • The rules are intact after the mailbox is converted to a shared mailbox.

Use the Classic Exchange admin center to convert a mailbox

  1. Go to the Classic Exchange admin center.

  2. Select Recipients > Mailboxes.

  3. Select the user mailbox. Under Convert to Shared Mailbox, select Convert.

  4. If the mailbox is smaller than 50 GB, you can remove the license from the user, and stop paying for it. Don't delete the user's account. The shared mailbox needs it there as an anchor. If you're converting the mailbox of an employee that's leaving your organization, you should take additional steps to make sure that they can no longer log in. For more information, see Remove a former employee from Microsoft 365.

Note

It's not required to reset the user's password during mailbox conversion. However, if the password is not reset, the original username and password continue to work after the mailbox conversion is finished.

For everything else you need to know about shared mailboxes, see About shared mailboxes and Create a shared mailbox.

Note

Shared mailboxes don’t require a separate license. However, if you want to enable In-Place Archive or put an In-Place Hold or a Litigation Hold on a shared mailbox, you must assign an Exchange Online Plan 1 with Exchange Online Archiving or Exchange Online Plan 2 license to the mailbox.

Use the New Exchange admin center to convert a mailbox

  1. Go to the Exchange admin center.

  2. Select Recipients > Mailboxes.

  3. Select the user mailbox. In the Mailbox tab, under More Actions, select Convert to shared mailbox.

  4. If the mailbox is smaller than 50 GB, you can remove the license from the user, and stop paying for it. Don't delete the user's account. The shared mailbox needs it there as an anchor. If you are converting the mailbox of an employee that is leaving your organization, you should take additional steps to make sure that they cannot log in anymore. Please see Remove a former employee from Microsoft 365.

Note

It's not required to reset the user's password during mailbox conversion. However, if the password is not reset, the original username and password continue to work after the mailbox conversion is finished.

For everything else you need to know about shared mailboxes, see About shared mailboxes and Create a shared mailbox.

Note

Shared mailboxes don’t require a separate license. However, if you want to enable In-Place Archive or put an In-Place Hold or a Litigation Hold on a shared mailbox, you must assign an Exchange Online Plan 1 with Exchange Online Archiving or Exchange Online Plan 2 license to the mailbox.

Convert the mailbox of a deleted user

After deleting a user account, follow these steps to convert their old mailbox to a share mailbox:

  1. Restore the user's account.

  2. Make sure a Microsoft 365 license is assigned to it.

  3. Reset the user's password.

  4. Wait 20-30 minutes for their mailbox to be re-created.

  5. Once the mailbox is re-created, remove the license from the user's mailbox. Don't delete the user's old mailbox. The shared mailbox needs it there as an anchor.

  6. Add members to the shared mailbox.

Convert a shared mailbox back to a user's (private) mailbox

  1. Go to the Exchange admin center.

  2. Select Recipients > Shared.

  3. Select the shared mailbox. Under Convert to Regular Mailbox, select Convert.

  4. Go back to the admin center. Under Users, choose the user account associated with the old shared mailbox. Assign a license to the account, and then reset the password.

    It will take a few minutes for the mailbox to get set up, but after that, the person who's going to use that account is ready to go. When they sign in, they'll see the email and calendar items that used to be in the shared mailbox.

Convert a user's mailbox in a hybrid environment

For more info about converting a user mailbox to a shared mailbox in an Exchange Hybrid environment, see:

Note

If you're a member of the Organization Management or Recipient Management role group, you can use the Exchange Management Shell to change a user mailbox to a shared mailbox on-premises. For example, Set-Mailbox -Identity mailbox1@contoso.com -Type Shared.

About shared mailboxes (article)
Create a shared mailbox (article)
Configure a shared mailbox (article)
Remove a license from a shared mailbox (article)
Resolve issues with shared mailboxes (article)