You need to re-key your certificate from GoDaddy
http://help.godaddy.com/topic/236/article/4976you have to enter the following domains
mail.domain.com (external facing FQDN)
autodiscover.domain.com (Create an entry in your godaddy DNS for autodiscover to point to your public IP)
mail.domain.local (FQDN of Exchange Server )
mailservername (mail server name)
You can use this tool to install it after that
www.u-btech.com/products/certificate-manager-for-exchange-2007.html