> Also, even if you both run your own MTAs STARTTLS does not help much except to reduce the scope of the passive-only surveillance dragnet, because the configuration does not require signed certificates.
Exim and Postfix (and hopefully others to come) are both working on adding DNSSEC and DANE support right now. Which means in the not too distant future it will be possible to publish cryptographically signed data in the DNS that your MX has TLS support, and what the fingerprints are.
> Finally, if both parties are technical enough to run their own email servers, um, why not just use GPG?
OpenPGP encrypted email leaks all sorts of information/meta data.
The metadata problem is so hard that if you actually solve it you are not using email anymore. This is why I'm saying it's a boondoggle. Even in the best case where my mother and I are running our own STARTTLS secured MTAs, oh wait, timing and message size.
GPG gives you actual privacy but minimal resistance against traffic analysis. All this other stuff gives you NO end to end privacy, AND minimal resistance against traffic analysis.
Messaging is a weird special case and GPG is behind the times (because people are coming to realise that repudiability and FS are important), but it's still a heck of a lot better than even working TLS slapped on SMTP (which doesn't even currently exist).
The security of email will never be perfect; that is obvious. But there is still legitimate and real value gained from making small incremental improvements to it. If you can hide the To/From/Subject of a message from a passive or even active MITM (because of DANE), then that's a good thing.
Exim and Postfix (and hopefully others to come) are both working on adding DNSSEC and DANE support right now. Which means in the not too distant future it will be possible to publish cryptographically signed data in the DNS that your MX has TLS support, and what the fingerprints are.
> Finally, if both parties are technical enough to run their own email servers, um, why not just use GPG?
OpenPGP encrypted email leaks all sorts of information/meta data.