A clarification: I only meant my suggestion to apply to the body of the
mail.  RFC822 already deals adequately (well almost) with folding headers.
The one place where it falls down happens when a "token" is longer than
79 characters (one blank must be at the beginning of a folded field).
Such tokens almost always come from systems using UUCP.  I also thought
of this suggestion yesterday, because someone sent me a TeX file in mail
which had some lines of length > 80.  There was no automatic way to put them
back together: I had to do it by hand.
                        Victor