ssh public keys instead of SASL for authenticated SMTP sending? I'm currently using postfix and SASL on my personal server for authenticated SMTP. The server is purely for my personal use and my personal domains, so I'd much rather have something simpler based on ssh public keys. Does any such solution exist?

While it isn't SSH's pubkey authentication (which is something that only exists in the SSH protocol, not SMTP), you could set up TLS Client certificates. This will require a valid SSL certificate on the client side.

Also, if you must use SSH's pubkeys, you could simply allow all mail connections from localhost on your personal SMTP server, and set up an SSH tunnel over SSH to port 25 on the SMTP server.