I had to go through the process today of regenerating expired Exchange 2007 certificates. The Exchange 2007 self-signed certificates expire every 12 months. Once the certificates expire, you will start to see event 12014 in the event logs. This is logged as an error and can be pretty annoying for those of us who hate seeing red in the event logs. If you have a third party certificate in place, there should be no impact to the end user. However, if you are relying on the built-in certificates for functionality there can be an effect to the end user since the certificate is expired. Read more