I've got an exchange server behind behind a port to address translation firewall. The server is reachable from the internet using a dyndns-url.

Now I want to sync windows phones to exchange mailboxes. To achieve this, I need to install the exchange certificate on the windows phone (send it to the phone by mail, double click). So far so good.
But, as far as I can see this does only work if the certificate on my exchange server matches the dyndns-url?

So I'd like to know: how do I create a self signed certificate for my dyndns-url and install it on exchange?