You create a user account in a child domain of a Microsoft Exchange Server 2010 forest. The forest has Exchange Server 2010 Service Pack 1 (SP1) Update Rollup 3 or a later update rollup installed.
The user does not have a mailbox.
You grant the user Full Access permission to a shared mailbox in a different domain.
The user logs on to the shared mailbox by using Microsoft Outlook Web App Premium.
The user tries to move or delete an item in the shared mailbox.
In this scenario, the user receives the following error message:
The Mailbox you are trying to access isn't currently available. Please try again in a few minutes.
This issue occurs because Outlook Web App Premium cannot create a security context if the user does not have a mailbox. When Outlook Web App Premium uses an Exchange Server 2010 Client Access server to redirect the request to another server, Outlook Web App Premium requires a mailbox to create a security context. However, because the user does not have a mailbox, a UserHasNoMailboxException exception is thrown.
To resolve this issue, install the following update rollup:
2661854 Description of Update Rollup 2 for Exchange Server 2010 Service Pack 2
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about a similar issue, click the following article number to view the article in the Microsoft Knowledge Base:
2489822 "The Mailbox you are trying to access isn't currently available" error when you use OWA Premium to try to delete an item that is in a shared mailbox