How to enable automatic downloading of Intermedicate Certificate - IIS 6.0?

I'm currently having some issues synching a Windows Mobile 5 device to an
Exchange 2003 server via ActivSync. It reports error 0x80070300. The
device was working at one time. The only difference between then and now is
the IIS certificate. Initially, the certificate was issued by VeriSign, but
now it's from a third-party Intermediate Certificate Authority. Because
it's a third-party certificate, I installed the Root and Intermediate
certificates in the root store of the mobile device.

I've tried multiple tests in an attempt to identify the root cause. Please
keep in mind that the server is currently serving successful requests (HTTP,
HTTPS, and RPC over HTTPS), just not to WM5. I've loaded all the required
certificates and CRLs on the server. To rule-out ActivSync specific issues,
I tried accessing the IIS root website via WM5 Internet Explorer, but also
receive the same error, 0x80070300.

After many attempts, I'm thinking that the root cause is a security
enhancement to IIS 6.0 in which is doesn't automatically download
Intermediate Certificates to clients, which brings me to my question: How
do I disable this feature?

-Intermediate Certificates Are Not Downloaded to Complete a Certificate
Chain
http://www.microsoft.com/technet/prodtechnol/WindowsServer20 03/Library/IIS/77cf4a99-9e0e-42be-8c2e-eaa4cb24c200.mspx?mfr =true

Miguel