While I agree in general that shorter emails are preferable - longer emails draw you in more and can really show that the sender has thought things through, thus making you more open to reciprocating.
That's why you include a URL. Otherwise, maybe put 3 lines up top, and more info below which could stand on its own.
I don't get anywhere near as much email as a professional investor, but unless it's from someone I know and actually want to hear from, or someone paying me, if it goes on for more than 3 lines without being compelling, I just hit delete.
