I am transitioning 2003 to 2010. Have done the CAS 2010 install. Have the dns updated. have the ssl cert on the 2010 and also exported and assigned to the 2003. have done the set Exchange2003URL link name to be the 2003 box. Internally, when I type in https://legacy.contoso.com/exchange i get the 2003 authenticate prompt and go right in to 2003 OWA When I type in https://mail.contoso.com/exchange it gives me the 2010 authenticate prompt but when I put in the info, it turns around and gives me another authenticate prompt ("connecting to legacy.contoso.com") and then when I put in my info again into this one it ends up giving me an http500 cannot be displayed error... with the address showing as: https://legacy.contoso.com/exchweb/bin/auth/owaauth.dll Any suggestions?