Software driver development - how to get drivers signed?

Hello,

my development team is in a very specific situation. We are developing an encryption app that would "sit" between an e-mail application and the world and encrypt/decrypt e-mails on the fly.

To do this seamlessly, we came up with the idea of a kernel-side driver that filters the traffic. Technically, it can be done, we already have a working prototype.

But how to sign that driver by Microsoft? Every single source of information that concerns signing drivers targets hardware manufacturers only. How can we even begin the process of applying? There is no one to talk to, not a single page that would address the topic - or I haven't found it yet.

Thanks for any tips.