My mail server forces TLS and strong ciphers. Try it out. postmaster@ohdns.org

You may also test using that address on checktls[1]

[1] http://www.checktls.com/perl/TestReceiver.pl?ASSURETLS

I receive emails from whitehouse.gov and other .gov sites just fine, so they seem to be ok with it.

Also, my self signed CA cert and self signed server cert regenerate every hour for those that do not support PFS. My DH primes regenerate periodically. If you are someone that needs to assure you are talking to me, you don't need a CA. Instead, you test the connection to me from multiple ISP's before and after you send me an email.

For real security, you would encrypt the payload. Maybe an encrypted 7zip inside a PGP encrypted message.