One for me to refer back to in the future in case it ever happens again. We had a new Microsoft Exchange 2013 server installed during the school summer holiday and due to the school changing its name to "The De Montfort School", I had to purchase a new wildcard certificate for the domain tdms.worcs.sch.uk.
Anyway, after applying for the certificate, and eventually installing it, I got the message "Revocation Check Failed"
To cut a long story short, when running the following from a command prompt, I received this.....
C:\>netsh winhttp show proxy
Current WinHTTP proxy settings:
Direct access (no proxy server).
Essentially, Exchange wasn't using my servers proxy settings, so therefore could not contact the Revocation servers at Comodo (the supplier of our certificate).
Running the following command imports the proxy settings from Internet Explorer. Once done, the server could perform the Revocation checks, and all of my certificates are now showing as valid and working....
C:\>netsh winhttp import proxy ie
Current WinHTTP proxy settings:
Proxy Server(s) : 10.0.0.27:3128
Bypass List : (none)
Easy when you know how!!!!!!