Sharing an interesting Tip that will assist you to troubleshoot active sync in an Enterprise Environment. If you have lot of servers behind a CAS array & you suspect that there might be one of the server that can have issues, checking one by one each server with a mobile device is cumbersome so you can download the tools from below link.
One is EAS_MD : reference http://mobilitydojo.net/2010/03/30/rolling-your-own-exchange-activesync-client/
Launch it & add the server name one by one , click Basic connectivity Test.
if Result is PASS than Active SYnc is responding fine.
Other tool in the zip file is :
ActiveSyncTester: refrence https://store.accessmylan.com/main/diagnostic-tools
I like the first one the most as its fast for me to check 10-15 servers quickly.