I was able to install our Thawte SSL certificate, but some apps don't recognize the cert chain. E.g. Zimbra Desktop, Windows mobile devices, some proxy gateways.

I installed the Thawte cert in the commercial.crt file.
The commercial_ca.crt file has:

Thawte root cert
Thawte cross-root
Thawte intermediate

chained together.
Zimbra accepts this, but above devices prompt with cert error.
Any ideas?