It's basically like you described - an informally specified set of rules the various "big players" in e-mail enforce. There's some consensus about the things yo

It's basically like you described - an informally specified set of rules the various "big players" in e-mail enforce. There's some consensus about the things you "have" to do to participate in e-mail but it's generally not a black and white "do these things and you'll be fine" situation.