Who is your Certificate Authority and what type of Cert is it?
Windows Mobile devices recognize only a small # of Certificates (especially older Windows Mobile devices). If you are having issues connecting, the issue most likely is that the Cert you are using on your front end is not an accepted one for Windows Mobile devices.
See this: http://support.microsoft.com/kb/915840
To verify, you can request a ‘trial’ certificate from Thawte.com (SSL 123 type) and deploy. This is a fully functional cert for 30 days that is accepted by all Windows Mobile devices without having to force the device to accept it and the authority.
What is your OWA URL?
From: Todd Lemmiksoo
I'm have difficulty setting up Exchange ActiveSync in a single Exchange 2003 setup. The Exchange server is front ended by ISA2006 SE. I have read and used the article "How to Publish Microsoft Exchange Active Sync with ISA Server 2006" by Marc Grote. The error that the mobile device gets is "The security certificate on the server is invalid. Support Code : 0x80072f0d". I have the OWA certificate installed on the Exchange and ISA servers since Sept 2007. OWA has been working fine since that time. I think my problem is related to SPN for HTTP/owa.all-mode.com. Should this be on the Exchange or ISA server?
Any help is greatly appreciated.