After I installed Exchange 2013 and tried to access either OWA or ECP on it, I kept getting Error 500. Looking at the httpproxy logs, I saw this: The unhandled exception was: System.Security.Cryptography.CryptographicException: Invalid provider type specified.
Turns out Exchange doesn’t like the key provider, Microsoft Software Key Storage Provider, so you have to reissue a cert using Microsoft RSA SChannel Cryptographic Provider as the provider.
I did this by going through the web cert enrollment and using the Web Server template. Then I assigned the new certificate to the SSL sites in IIS.
The solution is over here.