have exchange 2010 and exchange 2013 in my environment. Migrating everyone from 2010 to 2013. 2010 server has all roles. 2013 deployment has 3 servers (2 cas and 1 MBX) I started having trouble with outlook for mac 2011 and some phones after moving everyone to 2013. I thought i had fixed the issues by increasing some of the throttling values on exchange 2013 server. I have also used the test connectivity website Microsoft offers. The exchange ews, notification test is successful against the 2010 server. It fails against the 2013 servers. The external URL's are configured correctly on the cas servers. I've included a snip of the error: <testresult status="Error" errorid="236ff98a-34b2-4bdd-b4dd-942887359316" contentUrl="" testdescription="Getting subscription events and confirming that the expected events exist." resultdescription="Events couldn't be retrieved or confirmed." additionaldetails="No notifications were returned.