The other day, one of my Exchange 2016 lab servers stopped working. Well, I say "stopped working" but most things seemed to be working except for the Exchange Management Shell where I would get the following error when opening it:
OWA and ECP were also not working: I would simply get a blank page after signing in...
In the event log, there were hundreds of 15021 event errors complaining about SSL configuration:
Log Name: System
Date: 17/05/2017 03:51:17
Event ID: 15021
Task Category: None
Description: An error occurred while using SSL configuration for endpoint 0.0.0.0:444. The error status code is contained within the returned data.
As you can imagine, problems with SSL connections can affect multiple Exchange components such as the shell, ECP and OWA in this case (and many others if I had checked I'm sure). These problems can be the result of certificates not installed or incorrectly installed, and should be deleted from the system and reinstalled with the appropriate information.
So, I checked the installed certificates on this server by running netsh http show sslcert:
Nothing suspicious at first sight, but then again, I can't remember the last time I ran this command so I wasn't exactly sure what to look for. Until I ran the same command on a healthy server and noticed that the certificates used for 443 and 444 were the same:
So I went back to the affected server, deleted the certificate assigned to 0.0.0.0:444 by running netsh http delete sslcert ipport=0.0.0.0:444 and assigned the same certificate as the one used on port 443 by running netsh http add sslcert ipport=0.0.0.0:444 certhash="certificate_hash" appid="application id":
Restarted the server and everything was back to normal! :)