When you have a Microsoft Exchange Server 2010 server, the UDP ports are depleted and the server loses connectivity. Additionally, the W3WP.exe process consumes most of the UDP ports on the server. When this issue occurs, users cannot connect to the server unless Exchange application pools are restarted.
Note You can run the netstat -ano cmdlet to check whether the server is listening to the active ports.
This issue occurs because socket leaks occur in Exchange application pools when the Exchange server encounters DNS query failures, such as in the MSExchangeServicesAppPool application pool.
To resolve this issue, install the following update rollup:
2803727 Description of Update Rollup 1 for Exchange Server 2010 Service Pack 3
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about the netstat cmdlet, go to the following Microsoft website: