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Article ID: 2710029 - Last Review: July 9, 2014 - Revision: 9.0


Assume that you have a hybrid deployment of Microsoft Exchange Online in Microsoft Office 365 and in your on-premises Microsoft Exchange Server environment. After directory synchronization runs, shared mailboxes that were moved from the on-premises environment to Office 365 are unexpectedly converted to regular mailboxes. When this happens, you may be unable to convert the mailboxes to shared mailboxes. If you can make this conversion, the mailboxes revert to shared mailboxes the next time that directory synchronization runs.

Additionally, when you view the properties of the shared mailboxes in the Office 365 portal, you may receive the following error message:
Exchange: Couldn't convert the mailbox because the mailbox <guid> is already of the type 'Regular'


This issue occurs if the value of the msExchRemoteRecipientType attribute isn't set correctly by the on-premises hybrid server that's running Microsoft Exchange Server 2010 Service Pack 1 (SP1).

In Exchange Server 2010 SP1, the value of the msExchRemoteRecipientType attribute is set to 0x4. A value of 0x4 indicates that the mailbox was migrated. In this scenario, directory synchronization replicates the attribute to the cloud, and then Office 365 converts the shared mailbox to a regular mailbox.

In Exchange Server 2010 Service Pack 3(SP3), the value of the msExchRemoteRecipientType attribute is set to 0x64. The hexadecimal value of 0x64 is equal to a decimal value of 100. In this scenario, the shared mailbox isn't converted to a regular mailbox when directory synchronization runs. Instead, it remains as a shared mailbox.


To resolve this issue, install Exchange Server 2010 SP3 on the on-premises Exchange 2010 hybrid server that you use to move mailboxes to Office 365. We strongly recommend this method because the value of the msExchRemoteRecipientType attribute of mail-enabled users will be set correctly when you move mailboxes to Office 365 in the future.

For mailboxes that are already affected, manually change the value of the msExchRemoteRecipientType attribute of the mail-enabled user from 4 to 100. Then, wait for directory synchronization to run, or manually force directory synchronization. This converts the mailbox to a shared mailbox.


To work around this issue, use one of the following methods, as appropriate for your situation.

Method 1

Warning This procedure requires Active Directory Service Interfaces Editor (ADSI Edit). Using ADSI Edit incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems that result from the incorrect use of ADSI Edit can be resolved. Use ADSI Edit at your own risk.

If installing Exchange 2010 SP3 isn't an option for your organization, you can use ADSI Edit to change the value of the msExchRemoteRecipientType attribute to 100. To do this, follow these steps:
  1. Open ADSI Edit, and then connect to the default naming context.
  2. Expand the domain, and then expand the organizational unit (OU) that contains the mail-enabled user object.
  3. Right-click the mail-enabled user object, and then click Properties.
  4. In Attribute Editor, locate and then select the msExchRemoteRecipientType attribute.
  5. Click Edit, type 100, and then click OK.

  6. Wait for directory synchronization to run, or manually force synchronization.
After you follow these steps, the mailbox is converted to a shared mailbox.

Important The side effect of manually setting the value of the attribute is that Exchange Server 2010 SP1 does not recognize 100 as a valid recipient type, and you will be unable to manage the object by using Exchange Management Console or Windows PowerShell. If the object is manipulated in any way while it's in this state, the value of the msExchRemoteRecipientType attribute will revert to 4.

Method 2

You can use the Microsoft Exchange Management Shell to change the value of the msExchRemoteRecipientType attribute of all users at the same time. To do this, follow these steps:
  1. Run the Exchange Management Shell as an admin.
  2. At the command prompt, type the following commands, and then press Enter:
    $mbx = Get-Mailbox -ResultSize Unlimited -Filter {(RecipientTypeDetails -eq "UserMailbox") -and (RemoteRecipientType -eq "Migrated")}
    $mbx | fl Name, *recip*
    $mbx | Set-Mailbox -RemoteRecipientType "ProvisionMailbox, ProvisionArchive"

    Note The ProvisionMailbox and ProvisionArchive flags set the msExchRemoteRecipientType attribute to the correct decimal value for the version of Exchange on which the Exchange Management Shell commands are running.


For more info about how to use ADSI Edit, go to the following Microsoft TechNet website:
ADSI Edit (adsiedit.msc) (
Still need help? Go to the Office 365 Community ( website.

Applies to
  • Microsoft Exchange Online
o365 o365022013 o365e o365m o365a hybrid KB2710029
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