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Mailbox type difference in Exchange hybrid

We see a mailbox with a different mailbox type in Exchange on-premises and Exchange Online. However, the mailbox type should be the same between both organizations in an Exchange hybrid deployment. Why is that happening, and how to correct this mailbox inconsistency?

Exchange mailbox type

Let’s look at the info mailbox (info@exoip.com) in both Exchange on-premises and Exchange Online.

The mailbox shows up in Exchange on-premises as a user mailbox.

Mailbox type difference in Exchange hybrid remote user mailbox

The mailbox shows up in Exchange Online – Office 365 as a shared mailbox.

Mailbox type difference in Exchange hybrid shared mailbox

Why is there an inconsistency between the mailbox in both organizations? Shouldn’t they be the same? Let’s find out more.

Why this happens

The Exchange on-premises server is the authority server. The mailboxes are created from the on-premises organization. That’s why you need to keep at least one Exchange Server on-premises in a hybrid deployment.

In an Exchange hybrid deployment, you create or edit a mailbox on the Exchange Server on-premises with the options:

If, for example, the info mailbox needs to change from user mailbox to shared mailbox in Exchange hybrid, you need to convert the mailbox from Exchange Management Shell on-premises. It’s not possible to do that from Exchange admin center on-premises. You set the remote mailbox type to shared. Do you want to set it from shared to a user mailbox? That’s possible. The only difference is that you choose the regular value.

In this case, they didn’t do it as the above steps. What did happen is that they converted the mailbox from user to shared in Exchange Online. That’s not correct as it will not write the changes back to Exchange on-premises.

So how do you fix it and make the info mailbox in both Exchange organizations the same mailbox type? Let’s look at that in the next step.

Solution for mailbox type difference in Exchange hybrid

Start Exchange Management Shell as administrator, which is on the on-premises Exchange server or on a Management server where you have the Exchange management tools installed.

Run the Get-RemoteMailbox cmdlet and verify the RecipientTypeDetails for the mailbox. The info mailbox shows as a RemoteuserMailbox.

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

Name     RecipientTypeDetails     RemoteRecipientType
----     --------------------     -------------------
Info     RemoteUserMailbox        ProvisionMailbox

Run the Set-RemoteMailbox cmdlet. Add the Type parameter with the value Shared. It will convert the remote mailbox to a shared mailbox.

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

Verify that everything is set and looks good with Get-RemoteMailbox cmdlet.

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

Name     RecipientTypeDetails     RemoteRecipientType
----     --------------------     -------------------
Info     RemoteSharedMailbox      ProvisionMailbox, SharedMailbox

Go back to Exchange admin center on-premises. The mailbox shows as shared. Just like in Exchange Online – Office 365.

Mailbox type difference in Exchange hybrid remote shared mailbox

Do you want to set the mailbox to a different type? The Type parameter specifies the type for the mailbox. Choose one of the valid values:

  • Regular
  • Room
  • Equipment
  • Shared

Read more: Office 365 mailbox not showing in Exchange hybrid on-premises »

Conclusion

In this article, you learned why there is a mailbox type difference in Exchange hybrid. The solution to the mailbox inconsistency in both Exchange organizations is to set the remote mailbox type from Exchange on-premises.

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 »

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