Many users are facing the issue.

Migration for user mailbox was completed obviously but users can't open mailbox due to the error.

Error

Cannot expand the folder. Microsoft Exchange is not available. Either there are network problems or the Exchange server is down for maintenance

And test connectivity for users shows for impacted mailbox,

it's shown failure and Exchange 2010, DB.

I guess that Global Catalog which user access has old information about Exchange 2010,

but user mailbox is already in Exchange 2013. That's the issue of replication.

 Have you ever heard the similar issue?

 

• Edited by tanale 21 hours 35 minutes ago

Hi ,

Have you tried reconfiguring the outlook profile ?

What happens in owa ?

OWA say something went wrong.

Outlook reconfigure can't solve this issue.

Hi ,

Is this issue is happening for all the users mailboxes moved from exchange 2010 to exchange 2013 ?

Have you checked the below links.

https://support.microsoft.com/en-us/kb/2992644?wa=wsignin1.0

http://www.techtalklive.org/ttlblog/Pages/Exchange-2010-2013-Coexistence.aspx

https://social.technet.microsoft.com/Forums/en-US/9a722f68-42f5-4a3f-84ff-93387402efa4/cannot-expand-the-folder-the-set-of-folders-cannot-be-opened-microsoft-exchange-is-not-available?forum=exchangesvrgeneral