So a couple weeks ago, what seemed like randomly, a majority of my Outlook clients stopped working. When Outlook is launched there is an error related to the security certificate. There is a problem with the proxy server's security certificate. The security certificate is not from a trusted certifying authority. Outlook is unable to connect to the proxy server XXXXXXX. (Error Code 8).
I don't know where I need to go to fix this. The mail server uses a self signed/generated certificate. We use auto discovery to configure the Outlook clients. I'm sure it is something easy but I can't figure it out. In the mean time we have been manually installing the certificate on all the client machines and putting it in the Trusted Root Authority store. The certificate has been in place at least a year and we used it, installed new outlook clients, added new users without any issue or errors. Now we get this error every time for every profile, even on machines that already had the certificate manually installed for a different user.
What do I need to change to fix this? I thought about forcefully installing the certificate via command in a login script but I figure there has to be an easier way on the server or related to auto discovery to fix this.