Exchange 2010 sp3 cu4 with Exchange 2013 CU8.
We switched autodiscover and CAS dns record webmail to the Exchange 2013 server.
All works well for users on Exchange 2010 and also some test users on Exchange 2013.

Now we have a shared mailbox/user mailbox that someone has full access to, from Exchange 2010 that we have migrated over to our 2013 environment.  After the migration, users on 2010 can no longer open the mailbox via Outlook.  They have all the proper permissions (full access on the mailbox)

We are using NTLM only to authenticate.  I've also set changed the shared mailbox to a 'shared mailbox' in Exchange 2013 but users still can't open it.

They recieve "Cannot open the folder.  The set of folders cannot be opened.  Microsoft Exchange is not available.  Either there are network problems or the Exchange server is down for maintenance."

I've found this > https://support.microsoft.com/en-us/kb/2834139 but this applies for users on 2013 that not can open a 2010 mailbox, our situation is the other way around so not applies to us.

• Edited by dirkverhagen123 Wednesday, June 17, 2015 5:41 PM

Hi,

Please confirm whether the Exchange 2013 can open the shared mailbox which is moved from Exchange 2010 to Exchange 2013.

Please remove the full access permission for the Exchange 2010 users. Then run the following commands in Exchange 2013 EMS to add the full access permission for Exchange 2010 users:

Add-MailboxPermission -Identity SharedMailbox -User Exch10User1 -AccessRights FullAccess

Then check whether the issue persists.

Regards,

Hi Winnie,

When the box is also moved to Exchange 2013 the user can open it.

Will try the remove permissions and set the permissions again in EMS 2013, but is this really necessary and thus a known bug in Exchange 2013?

As we have 5000+ mailboxes i prefer this not as a solution.

Regards,