I have a strange issue that just popped up. We moved a client from Google Apps for Business to a hosted Exchange environment last week for email. This client is new to us so I am not sure how their environment used to be. I setup an external autodiscover record just like I have for the rest of our hosted Exchange clients. When setting up Outlook for a user, autodiscover is finding an old certificate for mail.domain.com and throwing an alert. Everytime a user opens Outlook, the Security Alert attached appears. When I view the cert, it shows it expired in 2009. This only happens internally as I have tested outside the local network. I have checked DNS for any references to mail.domain.com and find none. Nothing returns when I ping mail.domain.com. I have checked IIS on all servers and certs for the local computer account and cannot find this cert referenced anywhere. There may have been an inhouse Exchange server at one point in time but there is not one any longer.
Any ideas would be greatly appreciated. Thanks!