Hi!

We've just upgraded from our old Domino email server to Office 365 E1 and running an on-premise Exchange 2013 hybrid server.

In Outlook 2013, when trying to expand a shared mailbox, It asks me to enter my outlook credentials. Trying so doesn't work and it continues to ask repeatedly. If I click cancel, I get the following error:

"Cannot expand 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."

The error only occurs in Outlook 2013 and it happens to all staff who are using Outlook 2013. Shared mailboxes are accessible in Outlook 2010 and OWA with no issues.

I have tried recreating profiles, removing and re-adding permissions, disabling auto-mapping. I've tested with creating shared mailbox in Exchange Online and on our hybrid server.

Hi,

Check if the kb below matches your scenario:

https://support.microsoft.com/kb/2992644

This problem occurs only when the following conditions are true:

• You are using Microsoft Outlook 2013 client version 15.0.4641.1001.
• The client is connected by using Outlook Anywhere (RPC over HTTP).

To resolve this issue, apply the update that is described in the following article in the Microsoft Knowledge Base:

2889859

If you are using the Click-to-Run version of Office 2013, the Outlook application is kept up to date automatically. For more information about Office 2013 Click-to-Run updates, see Microsoft Office 2013 Click-to-Run virtualization

I hope the information is helpful.

Regards,

Melon Chen
TechNet Community Support

Good day and thank you for your reply.

I've tried to apply KB2889859. It says I already have it installed. 

I'm currently running version 15.0.4659.1000 of Outlook 2013. It's connecting via HTTP. 

Issue still persists.

Did you find the answer for this. It seams to work for some users but not all.

thanks