I remember it being built-in to clients in the past. Certainly Evolution (Ximian, Novell, Gnome) did when I last used it half a decade ago. You could encrypt yo

I remember it being built-in to clients in the past. Certainly Evolution (Ximian, Novell, Gnome) did when I last used it half a decade ago. You could encrypt your message, sign it, and the other side would (if they had your public key) see a nice 'Signature verified' on the other side. It was a fairly smooth workflow except for having to type in your passphrase in for everything.