Email listener not reading emails. Error appearing in event viewer:
Customer should contact there exchange administrator.
Open EMC (Exchange Management Console). Select the Server Configuration node on the nav tree. Then right click the server and select properties. Open the "Limits" tab and configure the section labeled "Connection restrictions". I would recommend increasing the values rather than making them unlimited.
By default the settings are:
Maximum concurrent outbound connections: 1000 *Maximum concurrent outbound connections per domain: 20*
You will need to restart the Exchange Transport service when finished modifying these settings