One idea I had once was to write up an informational RFC called
"common mail submission APIs".
It would describe /bin/mail < message, /usr/lib/sendmail with the options
implemented in both SMAIL and PP (probably a small set) and anything
else that we could document well.
Of course, I have never gotten around to writing it.
In a tent, wearing an uniform, carrying a gun.....
Harald Tveit Alvestrand