1)Check whether you are using a self signed or thirdparty cert from IIS on the exchange server.
2) To check from the local system, follow these steps.
Start-run-type mmc and hit enter and MMC console will open.
Now click on File-add/remove snap in- click on add-certificates-computer accont and finish it.
Now you will see the certificates installed on the local machine. Check on the trusted root and intermediate certifcate whether we have the cert which is installed on the exchange server.
Keep me posted.
