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Convert user mailbox to shared mailbox in Exchange hybrid

Do you have an Exchange hybrid environment, and do you want to convert user mailbox to shared mailbox? That’s possible! But before you do that, check if the mailbox location is in Exchange Online (Microsoft 365/Office 365). If the answer is yes, you have to convert the user mailbox to shared mailbox from on-premises.

We already did write an article about how to convert user mailbox to shared mailbox. Follow the steps in that article if you have an Exchange on-premises environment or an Exchange hybrid environment with mailboxes located on-premises.

Convert user mailbox to shared mailbox

Let’s go through the steps to convert user mailbox to shared mailbox in an Exchange hybrid configuration.

1. Identify Exchange Online mailbox

Run Exchange Management Shell as administrator. Identify that the user mailbox is an Exchange Online mailbox with the Get-RemoteMailbox cmdlet.

[PS] C:\>Get-RemoteMailbox "Test.Mailbox1@exoip.com"

Name              RecipientTypeDetails     RemoteRecipientType
----              --------------------     -------------------
Test Mailbox1     RemoteUserMailbox        ProvisionMailbox

Try to run the Get-Mailbox cmdlet, and you will see that the mailbox cannot be found on-premises. Which is correct.

[PS] C:\>Get-Mailbox "Test.Mailbox1@exoip.com"
The operation couldn't be performed because object 'Test.Mailbox1@exoip.com' couldn't be found on
'DC01-2016.exoip.local'.
    + CategoryInfo          : NotSpecified: (:) [Get-Mailbox], ManagementObjectNotFoundException
    + FullyQualifiedErrorId : [Server=EX01-2016,RequestId=6bc6e4f0-8aa5-4a80-a7f4-8755e4af0ac8,TimeStamp=5/16/2021 9:1
   0:02 PM] [FailureCategory=Cmdlet-ManagementObjectNotFoundException] E674A159,Microsoft.Exchange.Management.Recipie
  ntTasks.GetMailbox
    + PSComputerName        : ex01-2016.exoip.local

Let’s have a look at how it looks in on-premises Exchange admin center. As you can see, it’s not possible to convert the Office 365 user mailbox to shared mailbox in on-premises Exchange admin center.

Convert user mailbox to shared mailbox in Exchange hybrid remote user mailbox.

In Microsoft 365 Exchange admin center, you will see the option to convert to shared mailbox in the details pane. When you click on the Convert to Shared mailbox link, it will successfully convert the mailbox to a shared mailbox. But, you should not do that!

Convert user mailbox to shared mailbox in Exchange hybrid user mailbox

Do not convert mailboxes in Microsoft 365 Exchange admin center when you have an Exchange hybrid environment.

The problem is that the on-premises object will still be a user mailbox because it will not write the changes back to the on-premises AD. The on-premises Exchange admin center will show as user mailbox, while in Microsoft 365 exchange admin center it will show as shared mailbox.

2. Run Set-RemoteMailbox cmdlet

Run the Set-RemoteMailbox cmdlet and specify the user mailbox. Make use of the -Type parameter and the Shared value. You can fill in the display name or email address of the mailbox. You will not get an output showing that it’s succeeded after running the cmdlet.

[PS] C:\>Set-RemoteMailbox "Test Mailbox1" -Type Shared

[PS] C:\>Set-RemoteMailbox "Test.Mailbox1@exoip.com" -Type Shared

The Shared value is available only in Exchange 2013 CU21 or later, Exchange 2016 CU10 or later, and Exchange 2019. In Exchange 2013 and Exchange 2016, you also need to run setup.exe /PrepareAD. For more information, see KB4133605.

Read more: Install Exchange Cumulative Update »

3. Force sync Azure AD

Force sync Azure AD Connect to have the changes apply to the cloud (Azure AD).

PS C:\> Start-ADSyncSyncCycle -PolicyType Delta

4. Verify converted mailbox type

It’s always good to verify your work. Check that the shared mailbox RecipientTypeDetails object shows the value RemoteSharedMailbox.

[PS] C:\>Get-RemoteMailbox "Test.Mailbox1@exoip.com"

Name              RecipientTypeDetails     RemoteRecipientType
----              --------------------     -------------------
Test Mailbox1     RemoteSharedMailbox      ProvisionMailbox, SharedMailbox

Look in on-premises Exchange admin center. The mailbox shows up in the shared mailboxes list. The details pane will show that it’s a Remote shared mailbox.

Convert user mailbox to shared mailbox in Exchange hybrid remote shared mailbox

In Microsoft 365 Exchange admin center, the mailbox shows as Shared mailbox.

Convert user mailbox to shared mailbox in Exchange hybrid shared mailbox

Suppose you use the new Microsoft 365 Exchange admin center. Go to Recipients > Mailboxes. Filter on Shared mailbox. It shows the recipient type Shared mailbox.

Convert user mailbox to shared mailbox in Exchange hybrid shared mailbox

5. Remove Exchange Online license

The user mailbox most likely has a license because it was a user mailbox. You can remove the Exchange Online license from the shared mailbox. But, before you do that, check if the mailbox size is greater than 50 GB. If the mailbox size is greater than 50 GB, you need to keep the Exchange Online license. Otherwise, you can’t send and receive mail from the shared mailbox.

A user must have an Exchange Online license to access a shared mailbox, but the shared mailbox doesn’t require a separate license. Without a license, shared mailboxes are limited to 50 GB. To increase the shared mailbox size limit to 100 GB, you must assign an Exchange Online Plan 2 license or an Exchange Online Plan 1 license with an Exchange Online Archiving add-on license.

Sign in to Microsoft 365 admin center. Go to Users > Active users. Click on the user and remove or change the license. In our example, we assign Office 365 licenses with Azure group-based licensing, and we need to adjust it from there.

Keep reading: Get shared mailbox size in Office 365 with PowerShell »

Conclusion

In this article, you learned how to convert user mailbox to shared mailbox in Exchange hybrid. Start Exchange Management Shell and run the cmdlet, as seen in the article. After that, verify the recipient type details. It will show as remote shared mailbox.

Did you enjoy this article? You may also like Create Office 365 shared mailbox in Exchange hybrid. Don’t forget to follow us and share this article.

ALI TAJRAN

ALI TAJRAN

ALI TAJRAN is a passionate IT Architect, IT Consultant, and Microsoft Certified Trainer. He started Information Technology at a very young age, and his goal is to teach and inspire others. Read more »

This Post Has 8 Comments

  1. Hi,

    I have a question: How to switch from a shared mailbox to a user mailbox?

    Will running the following command work?
    Set-RemoteMailbox “Test.Mailbox1@exoip.com” -Type Regular

    Is there anything else to think about besides re-issuing the license?

    Thank you very much for this site. I have solved many issues with my hybrid infrastructure.

    1. Hi Odo,

      I am glad that you find my site helpful.

      That command is correct. It will change the mailbox to a regular user mailbox. Nothing else to think about besides licensing the mailbox.

      If this is an Exchange hybrid environment, you might want to use the Set-RemoteMailbox cmdlet instead.

  2. Your article is very informative and useful. I do have a question for you. We do have a hybrid environment and we have never use “Shared” mailbox on prem. We always create a user mailbox and use it as “Shared” mailbox instead. Now, we are migrating all the user mailbox to Exchange Online and will need to change some of the on-premises user mailbox to “Shared” mailbox so that it won’t takes up an Office 365 license. I have two options here. 1. Change the on-premises user mailbox to on-premises shared mailbox and then migrate it over the Exchange online and end up with Office 365 shared mailbox. 2. Migrate the user mailbox to Exchange online and then covert the user mailbox to shared mailbox on Microsoft 365 Exchange admin center. What do we loose or real issues if we go with option 2 when the on-premises object is still be a user mailbox? We did a test, and the test mailbox is shown as “Shared” mailbox under Microsoft 365 Exchange admin center while it shown as “Remote User” mailbox under on-premises Exchange admin center. The test mailbox is operational and can send/receive emails without any issues. What are the real issues there?
    Thank you!

    1. Both the options you explained are correct. In your case, there are no mail flow issues. Everything will work as expected.

      There is only a mailbox type difference in the Exchange hybrid environment. Follow the steps in that article on setting the remote mailbox value if it’s not showing the same between on-premises and the cloud.

      The next time, convert the Office 365 mailbox from Exchange Management Shell on-premises. That way, the mailbox type will show the same in Exchange Admin Center on-premises and Exchange Admin Center in Exchange Online.

  3. What if this was done in the O365 admin center by mistake? Do we just run the command on premise to fix it? Right now user shows shared online by usermailbox on prem.

  4. Hi
    I have followed your article and everything has worked as expected up to the point of verifying that mailbox is classed as a Shared mailbox in M365. I have performed the delta sync and its been nearly 24hrs but the mailbox is still showing as a UserMailbox in M365. Exchange on prem sees it as a remote shared mailbox.
    Name RecipientTypeDetails RemoteRecipientType
    —- ——————– ——————-
    Services RemoteSharedMailbox Migrated, SharedMailbox

    1. Hi Steve,

      Something is going wrong. Try to do it with a test account and verify that it works.

      For the account that you mentioned, it’s set correctly in Exchange on-premises. You can convert the mailbox in Exchange Microsoft 365 Exchange admin to make the mailbox type similar.

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