Thanks to everybody who answered my query about the Dutch friend's
problem.  There seem to be two answers -- 1) any line more than 70
characters long -- especially uninterrupted characters -- upsets some
mailers.  2) certain mailers recognize a line of equal signs as the
division between two separate mail messages.  Both might apply in the
case I mentioned, though 2 seems to be the particular focus of the
Dutch friend's explanation.  -- Kevin Berland for C18-L