We have an in house Exchange 2010 setup, 1 CAS/HUB Server, 1 Mailbox Server, 1 ADFS Server and a DirSync Server. Over the last 2 weeks random clients have been experiencing an issue where they no longer are receiving new emails through outlook and all of the inbox folders now show the double blue arrows of a shared folder. It's happened to 5 client computers now. This is only affecting that install of outlook as they are not having issues when logged in via OWA, a terminal server or through their phones.
Looking for any idea of where to start looking as to the cause of this issue.