Hi Bert,

> 
> Seems you missed my earlier mail.
> 
> Firefox does include the root certificate:
> 
> 	http://www.mozilla.org/projects/security/certs/included/#T-Systems
> 
> But your server needs to send out the complete certificate chain, including the DFN certificate. See FAQ #7:
> 
> 	https://www.pki.dfn.de/faqpki/faqpki-mozilla/

Thanks,
will pass that on.

So Long,
	-Tobias