setting up s/mime

[ED]

Hi,

I wanted to setup S/MIME for all the users in the organization, but I've encountered a few problems.

1. Does GAM allows to upload a certificate for all the users at once?
2. How do I get a certificate?
3. If I setup S/MIME certificates for the whole domain, do I have any reason to let users upload their own certificate? 

Thanks,

Elad.