Exchange 2007 SP1 and Windows Mobile 6 clients

I have a single server (Exchange 2007 SP1) and have port 443 opened to the
Exchange server. I have the outside url for Activesync set up as
sync.domain.com.

I put this in the address field on the WIndows Mobile 7 clients and it says
it sync could not be completed. I have the Server set to use SSL and I have
the box checked for the same on the client device.

Am I missing a port or is there somethign else I need to do?

Thanks