Convert an Exchange mailbox to a shared mailbox

Last reviewed on June 26, 2014   —  5 comments

After a user quit, an administrator wanted to convert the mailbox to a shared mailbox, to free up the license the mailbox was using. Because the user handled important communications, he didn’t want to delete the mailbox right away.

While I’d export the mailbox to a pst for backup, delete it and add the user’s address(es) to the mailbox of the person who took over the job, it is possible to convert a mailbox to a shared mailbox.

Because shared mailboxes are limited to 5 GB on Office 365, you first need to reduce the quota to 5GB. If the mailbox is larger, you’ll need to move content to a pst file or delete it. If the mailbox has an online archive, export it to a pst file.

Set-Mailbox -ProhibitSendReceiveQuota 5GB -ProhibitSendQuota 4.75GB -IssueWarningQuota 4.5GB
Set-Mailbox -Type shared

The Type parameter supports Regular, Room, Equipment, and Shared as values.

Verify the mailbox is now a shared mailbox:

Get-Mailbox -Identity | Format-List RecipientTypeDetails

use PowerShell to convert a mailbox type

After converting the mailbox, give other users Full Access and Send As permission as needed. You can do this from the Exchange Control Panel or using PowerShell.

To use PowerShell to give a user or group FullAccess rights:

Add-MailboxPermission username -User newuser -AccessRights FullAccess

To use PowerShell to give a user or group SendAs rights:

Add-RecipientPermission username -Trustee newuser -AccessRights SendAs

Assign fullaccess and send as permissions to the shared mailbox

Now you can remove the license from the account in Users and Groups. Two dialogs will warn you that removing the license will delete the mailbox and the contents, however, because you converted the mailbox to a shared mailbox before removing the license, the mailbox won't be deleted. Note: while the mailbox contents are safe, Lync contacts may be lost.

The first dialog:
Are you sure you want to delete the license

The second dialog reads:

Are you sure you want to remove the Exchange license?

The user’s mailbox and all messages in it are deleted. We recommend that you only delete licenses from users who no longer need email.
All email aliases associated with the user account are deleted. If you need someone in your company to receive email at those aliases, assign them to another user.
Their Lync Contacts list may be deleted. To restore their Lync Contacts, assign the user an Exchange license within 30 days. If you want to remove their Exchange license but keep their Lync Contacts, contact Support before you remove the Exchange license.

More Information

More information is available at Convert a Mailbox (TechNet)

Written by

Diane Poremsky
A Microsoft Outlook Most Valuable Professional (MVP) since 1999, Diane is the author of several books, including Outlook 2013 Absolute Beginners Book. She also created video training CDs and online training classes for Microsoft Outlook. You can find her helping people online in Outlook Forums as well as in the Microsoft Answers and TechNet forums.

Please post long or more complicated questions at Outlookforums.

5 responses to “Convert an Exchange mailbox to a shared mailbox”

  1. Adam

    This was a very useful article, being the first time I've needed to perform such a task. Thank you!

  2. Mike

    great article!!! especially for a novice like me. i do have to say though i am lost at the last part where you say

    "Now you can remove the license from the account in Users and Groups."

    where is that done? i can't find it

  3. Avinash Illindra

    Thanks for the great article, it will be very helpful article.

    I have a small doubt on Second dialog:

    We lost the mails surely or is there any alteration for without loosing mails.

    Avinash Illindra

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