When installed and configured Exchange and/or Lync and would like to test the configuration on the outside of your network or you receive error messages from users u can use the following tool:
I’m going to test the Exchange Active sync settings using my own Exchange server.
I have filled the appropriate fields with the information asked for and then verify my account.
Now the account is being tested on my own Exchange server. After a while I receive the result and as you can see everything is OK, but when there are problems you will receive a detailed error with a link to the suggested solution on the Microsoft site.