I am pretty much having a very similar problem here:
https://social.technet.microsoft.com/Forums/exchange/en-US/437c5f8d-3a42-4689-90b4-13fd2749373f/go-daddy-ucc-certificate-exrca-can-only-validate-the-certificate-chain-using-the-root-certificate?forum=exchangesvr3rdpartyappslegacy
When I set up in outlook, I have noticed this in advanced connection settings:
the URL is required
mail.ex4.secureserver.net
Then check connect SSL only
Only connect to proxy servers with this principal name
msstd:mail.ex4.secureserver.net
When I use the connect principal, it works fine, but otherwise if it is not checked, it won't connect to the server.
http://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/Q_26423254.html
However, when I restart outlook, because I have multiple exchange accounts, they keep becoming "unchecked".
Everything worked fine about 48 hours ago, and now... all these problems.
Here is my log from the testing site:
Connectivity Test Failed
Test Details
Testing Outlook connectivity.
The Outlook connectivity test failed.
Additional Details
Elapsed Time: 3897 ms.
Test Steps
Testing RPC over HTTP connectivity to server mail.ex4.secureserver.net
RPC over HTTP connectivity failed.
Additional Details
HTTP Response Headers:
Content-Type: text/html
Server: Microsoft-IIS/7.5
WWW-Authenticate: Negotiate,NTLM
X-Powered-By: ASP.NET
Date: Fri, 13 Feb 2015 01:07:27 GMT
Content-Length: 58
Elapsed Time: 3897 ms.
Test Steps
Attempting to resolve the host name mail.ex4.secureserver.net in DNS.
The host name resolved successfully.
Additional Details
IP addresses returned: 72.167.83.115
Elapsed Time: 95 ms.
Testing TCP port 443 on host mail.ex4.secureserver.net to ensure it's listening and open.
The port was opened successfully.
Additional Details
Elapsed Time: 110 ms.
Testing the SSL certificate to make sure it's valid.
The certificate passed all validation requirements.
Additional Details
Elapsed Time: 461 ms.
Test Steps
The Microsoft Connectivity Analyzer is attempting to obtain the SSL certificate from remote server mail.ex4.secureserver.net on port 443.
The Microsoft Connectivity Analyzer successfully obtained the remote SSL certificate.
Additional Details
Remote Certificate Subject: CN=mail.ex4.secureserver.net, O="Starfield Technologies, LLC.", L=Scottsdale, S=AZ, C=US, Issuer: SERIALNUMBER=10688435, CN=Starfield Secure Certification Authority, OU=http://certificates.starfieldtech.com/repository,
O="Starfield Technologies, Inc.", L=Scottsdale, S=Arizona, C=US.
Elapsed Time: 356 ms.
Validating the certificate name.
The certificate name was validated successfully.
Additional Details
Host name mail.ex4.secureserver.net was found in the Certificate Subject Common name.
Elapsed Time: 0 ms.
Certificate trust is being validated.
The certificate is trusted and all certificates are present in the chain.
Test Steps
The Microsoft Connectivity Analyzer is attempting to build certificate chains for certificate CN=mail.ex4.secureserver.net, O="Starfield Technologies, LLC.", L=Scottsdale, S=AZ, C=US.
One or more certificate chains were constructed successfully.
Additional Details
A total of 1 chains were built. The highest quality chain ends in root certificate OU=Starfield Class 2 Certification Authority, O="Starfield Technologies, Inc.", C=US.
Elapsed Time: 39 ms.
Analyzing the certificate chains for compatibility problems with versions of Windows.
Potential compatibility problems were identified with some versions of Windows.
Additional Details
The Microsoft Connectivity Analyzer can only validate the certificate chain using the Root Certificate Update functionality from Windows Update. Your certificate may not be trusted on Windows if the "Update Root Certificates" feature isn't enabled.
Elapsed Time: 5 ms.
Testing the certificate date to confirm the certificate is valid.
Date validation passed. The certificate hasn't expired.
Additional Details
The certificate is valid. NotBefore = 11/29/2012 8:39:18 PM, NotAfter = 11/29/2015 8:39:18 PM
Elapsed Time: 0 ms.
Checking the IIS configuration for client certificate authentication.
Client certificate authentication wasn't detected.
Additional Details
Accept/Require Client Certificates isn't configured.
Elapsed Time: 232 ms.
Testing HTTP Authentication Methods for URL https://mail.ex4.secureserver.net/rpc/rpcproxy.dll?mail.ex4.secureserver.net:6002.
The HTTP authentication methods are correct.
Additional Details
The Microsoft Connectivity Analyzer found all expected authentication methods and no disallowed methods. Methods found: Negotiate, NTLM
HTTP Response Headers:
Content-Type: text/html
Server: Microsoft-IIS/7.5
WWW-Authenticate: Negotiate,NTLM
X-Powered-By: ASP.NET
Date: Fri, 13 Feb 2015 01:07:27 GMT
Content-Length: 58
Elapsed Time: 146 ms.
Attempting to ping RPC proxy mail.ex4.secureserver.net.
RPC Proxy was pinged successfully.
Additional Details
Elapsed Time: 224 ms.
Attempting to ping the MAPI Mail Store endpoint with identity: mail.ex4.secureserver.net:6001.
The attempt to ping the endpoint failed.
Tell me more about this issue and how to resolve it
Additional Details
The RPC_S_SERVER_UNAVAILABLE error (0x6ba) was thrown by the RPC Runtime process.
Elapsed Time: 2626 ms.