Article ID: 2710029 - View products that this article applies to.
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 occurs, 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.
Also, 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. The value of the msExchRemoteRecipientType attribute is incorrectly set to 0x4. A value of 0x4 indicates that the mailbox was migrated. In this situation, directory synchronization replicates the attribute to the cloud, and then Office 365 converts the shared mailbox to a MailUser object.
The value of the msExchRemoteRecipientType attribute should be set to 0x64. The hexadecimal value of 0x64 is equal to a decimal value of 100. In this situation, the shared mailbox isn't converted to a regular mailbox when directory synchronization runs. Instead, it remains as a shared mailbox.
To work around this issue, use the Exchange Management Shell to change the value of the msExchRemoteRecipientType attribute.
Change the value of the msExchRemoteRecipientType attribute for one userTo change the value for one user, follow these steps:
Change the value of the msExchRemoteRecipientType attribute for all usersTo change the value this for all users, follow these steps:
This is a known issue. Microsoft is currently investigating the issue and will post more information in this article when it becomes available.
Still need help? Go to the Office 365 Community
(http://community.office365.com/)website or the Exchange TechNet Forums