An excellent resource for Microsoft Exchange Server and Exchange Online administrators and consultants is the Remote Test Connectivity website at http://exrca.com or https://testconnectivity.microsoft.com/.
Here I am going to document an error that indicated that the Exchange Server (in this case) was not working, but we could see that the phone was connecting fine to the server. The error we say was:
“The certificate couldn’t be validated because SSL negotiation wasn’t successful. This could have occurred as a result of a network error or because of a problem with the certificate installation.”
“The Microsoft Connectivity Analyzer wasn’t able to obtain the remote SSL certificate”
The error looked like the following:
This error occurs when TLS 1.0 is disabled either on the end server or on a load balancer in front of the server. In my case this as the case with the Kemp load balancer we were using – TLS 1.0 was disabled under SSL Properties. Once we restored TLS 1.0 the Remote Connectivity Test tool, the tool worked instantly: