You may have Microsoft Exchange 2010/2013 users who are timing out, reconnecting, getting errors after a certain amount of time, this is due to the built-in system in the virtual Load Balancer.
To fix this issue you will need to increase your Server and Client timeout values.
You can do this in the Balancer -> Configuration -> Default Settings.
Once in Default Settings, you will then need to change both Server and Client Timeouts to 300,000.
That should have solved the issue but if it continues to be a problem then feel free to contact us at firstname.lastname@example.org.