Certificates between Blackberry and exchange server 2003

Hi all,
We are running an exchange 2003 server environment.Microsoft office outlook uses a certificate for successfull authentication with the server whilst ouside of the LAN.I am trying to setup and email mailbox on my new blackberry but it is unable to authenticate even though i installed in it the certificate that i use for my normal outlook.The error message i get on the Blackberry is that “The email account could not be validated”. I suspect its an authentication issue between the Exchange server and the outlook client on the Blackberry.Can someone please tell me if im on the right track or if someone has encoutered this before, how was the problem resolved so that i can synchronise between the BB and the server using certificates.