You have your choice of two reasonable choices:
LF|CRLF|CR: This works with any OS that purports to save files in ASCII
CRLF: This is what a standard does normally.
If it's LF|CRLF|CR, you can assume that it'll be saved that way on the file
system and the mail server can just read this file.
If it's CRLF, Unix and Mac users won't be able to just drop in a new
filter; they'll have to run a conversion program. (So it's a syntax
checker too; this isn't necessarily a bad decision.)
What's in the draft, as I had intended it (not that I've read the draft
recently, not that it's without error) is that a newline is any of the
three and an implementation is required to turn them into a CRLF when
printing out a message for servers. This is what made *me* happy; it is by
no means the right solution.
I feel like a skunk for arguing this and not just conceding that
all-the-world-is-either-CRLF-or-should-be, but I'm going to anyway.