In environment using Exchange 2013 [2 mailbox & CAS server] - 1 Database.
Suddenly user getting a error " There are too many active sessions connected to this mailbox. Please close other open instances and try to sign in again after a few minutes " after logging into OWA .
Note: As of now only 1 user getting this error , quite confused whether it will spread to other users.
Plese help me to resolve this issue