Using testexchangeconnectivity I got the following error:
Attempting FolderSync command on ActiveSync session
FolderSync command test failed
Exchange ActiveSync returned an HTTP 500 response.
You may get the following error when syncing your mobile phone or using www.testexchangeconnectivity.com. This error can be caused by many different issues. If you’ve tried everything, have a look on the virtual directories and check that the IP settings are not set to DENY for certain IP addresses. This was the cause of my pain recently.
Installing SBS SP1 on SBS Server will cause the deny ip settings to be inserted. Only local IP addresses were granted access on the exchange-oma and exchange directories.