So, then, what are the issues with S/MIME? Thunderbird supports it. Apple Mail supports it. Gmail does (but not for free accounts). It's the core of the DIREC

So, then, what are the issues with S/MIME? Thunderbird supports it. Apple Mail supports it. Gmail does (but not for free accounts). It's the core of the DIRECT Messaging protocol we use in healthcare. There are millions of messages being sent via DIRECT every week. Mind, DIRECT is more than just S/MIME, it's a just a component of it (there's an entire trust system involved as well). I appreciate the issue with leakage, which are very real, mostly due to the UI of the systems. I honestly don't know how well the programs like Apple Mail et al keep you from shooting yourself in the foot with S/MIME encrypted mail (such as "You're about to forward an encrypted email in the clear, are you sure you want to do that?"). The post bags on PGP, so I'm just curious if there are weaknesses inbuilt to S/MIME.