ISA 2004 + Exchange and access to mail with Windows Mobile

Hi

I have this network:
- An Windows 2003 Server / AD / DNS / Exchange 2003 server on the LAN
- An ISA 2004 Server in DMZ
- I have Qtec phones with Windows Mobile and 3G / GPRS

I'm trying to check my emails using push/pull technology.

I have made a rule/policy at the ISA2004 server that gives me access to OMA and Microsoft-Server-Activesync.

I have also bought a SSL-ceritificate.

Outlook webaccess via the ISA server works fine

I also manage to access https://official-host/oma and https://official-host/Microsoft-Server-Activesync with a browser, and it works fine. It prompts me with username/password as expected. I get a really basic html-version of my inbox/calendar etc.

However, I recieve the following error on my Windows Mobile phone: "Synchronization failed. Try again later. Error code: INTERNET_55.

I have tried various settings both on the ISA server and the Exchange server, and the error message on the phone change. Sometimes I get HTTP_404 or something, but then the URL-s specified above does not longer work with a browser.

I hope anyone have any idea what could be wrong.

regards
Frode Slettum