When your trying to launch EXfolders if you see the error
An error occurred while trying to establish a connection to the Exchange server. Exception: The Active Directory user wasn't found.
This is caused by a 2003 to 2010 migration where its looking at the old administrative group.
If this is the case open adsiedit.msc on the exchange server.
Open Configuration, Services, Microsoft Exchange, CN=Your Company, Administrative Groups
In here you see 2 folders. Of which each will have a CN=servers folder. One will be empty as this is the old group. Simply delete the empty CN=Servers folder and your good to go 🙂