Personal SSL certs and signed/encrypted email are not supported at this time. Those using them are generally creating PGP public/private keypairs and managing them personally.

Unofficial options:

Cleopatra and
GpgOL plugin with Outlook to sign/encrypt email others use
Enigmail with Thunderbird

Again, none of this is supported by IT Pros or by email admins so people are on their own as far as support.