Self-Signed Certs on Nokia E51

I have a Nokia E51 which I would like to setup Mailforexchange on to connect to use push email. Exchange is 2003sp2 and Active sync is setup, we have one iphone working off it at the moment.

When I try to connect the E51 web browser to our OWA https website just to make sure I can get to it I get the message "web unable to perform operation" but I can connect to other websites. We have a self-signed web cert created using SelfSSL and I did read somewhere that the S60 devices do not use self-signed cert so would I better buying a trusted cert from godaddy or somewhere like that.

Cheers

Derek.