Unable to connect using Exchange ActiveSync due to Exchange resource consumption

Which devices are suspect?
Usually if a device is sending over 1000 requests per day, we recommend investigating.

If the hits (requests) are above 1500, there could be an issue on the device or environment. The device and the user’s activity should be investigated. 

See the following post from the Exchange Team blog and .PS1 file that can be used with Windows Powershell to parse IIS log files for any version of Exchange Server.

A script to troubleshoot issues with Exchange ActiveSync
http://blogs.technet.com/b/exchange/archive/2012/01/31/a-script-to-troubleshoot-issues-with-exchange-activesync.aspx

ActiveSyncReport script
http://gallery.technet.microsoft.com/scriptcenter/ActiveSyncReport-script-a2417a84

Log Parser can be used without the script, but the script was designed to filter based on criteria specified in the command line used.  Using the script above, e-mail alerts or reports can also be created.

Steps that will assist administrators while troubleshooting:

The following options will not resolve the issue.  They will give you more time to parse through the IIS logs to determine the devices are suspect.

• Reduce the Keep Alive time value on the Exchange Mailbox servers to send a keep alive every 30 minutes to CAS instead of every 2 hours.
  
  The Keep Alive Value set to 30 minutes (1800000) in the registry, discussed in the following article in the Microsoft Knowledge Base online:
  http://support.microsoft.com/kb/324270  
  
  The Registry value information is below:
  Path: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters\
  Value name: KeepAliveTime
  Value Type: REG_DWORD-Time in milliseconds
                      Valid Range: 1-0xFFFFFFFF
                      Default: 7,200,000 (two hours)
  
  This value controls how frequently TCP tries to verify that an idle connection is still intact by sending a keep-alive packet. If the remote computer is still reachable, it acknowledges the keep-alive packet. Keep-alive packets are not sent by default. You can use a program to configure this value on a connection. The recommended value setting is 1,800,000 (equal to 30 minutes). (Decimal) (Requires Server restart)
  
  Monitor this setting and if the server ports are still being exhausted, then this may need to be lowered to 15 minutes instead of 30 minutes.
  
• Increase the IIS Connection Timeout in IIS
  
  The default and recommended value should be 120 seconds. If it is set at a higher value, then it should be set between the 120 seconds minimum recommended value to the 300 second maximum value.
  See the following topic in TechNet online for more information:
  
  http://technet.microsoft.com/en-us/library/cc182260.aspx
  
  This can be done by via the Properties of the Default Web Site by modifying the Connection Timeout value (in seconds).
  
• Increase the number of IIS connections (Queue Length) for the ExchangeApplicationPool on the Exchange 2003 Mailbox and Front-end servers:
  
  
  Use Internet Information Services Manager to turn off worker process recycling in IIS 6.0
  1.   Start Internet Information Services (IIS) Manager.
  2.   Expand the local computer, expand Application Pools, right-click the ExchangeApplicationPool application pools, and then click Properties.
  3.   Click to clear the Recycle worker processes (in minutes) check box, and then click OK.
  
  Use Internet Information Services Manager to increase the queue length in IIS 6.0
  1.   Start Internet Information Services (IIS) Manager.
  2.   Expand the local computer, expand Application Pools, right-click the ExchangeApplicationPool application pool, and then click Properties.
  3.   Click the Performance tab, and then modify the value in the Request queue limit box. Replace the default value of 1000 with 4000.
  4.   Click OK.
  
• Increase the number of IIS connections (Queue Length) for the MSExchangeSyncAppPool on the Exchange 2007 and Exchange 2010 Client Access Servers
  
  Use Internet Information Services Manager to turn off worker process recycling in IIS 7.0 and above (This should be disabled by default for the MSExchangeSyncAppPool)
  
  1. Start Internet Information Services Manager.
  2. Expand the local computer, and then click Application Pools.
  3. In the Application Pools pane, click the appropriate application pool, such as MSExchangeSyncAppPool or the new application pool that you created, and then click Advanced Settings.
  4. In the Recycling section, modify the Regular Time Interval (minutes) value. Replace the default value of 1740 with 0 (zero). A value of zero turns off worker process recycling.
  5. Click OK.
• Use Internet Information Services Manager to increase the queue length in IIS 7.0 and above
  
  1. Start Internet Information Services Manager.
  2. Expand the local computer, and then click Application Pools.
  3. In the Application Pools pane, click the appropriate application pool, such as MSExchangeSyncAppPool or the new application pool that you created, and then click Advanced Settings.
  4. In the General section, modify the Queue Length value. Replace the default value of 1000 with 10000.
  5. Click OK

NOTE: If running Exchange 2007 on Windows 2003 (IIS 6), follow the steps above to increase the Request Queue limit for the MSExchangeSyncAppPool.

For more information on why it may be important to change these values for Application Pools and for additional links to “How To” information, see the following topic from TechNet online:

http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/9701f9dd-d40b-4d24-a2df-1d1abc13f764.mspx?mfr=true