As required by RFC 2045 (MIME). The 78 byte lines work in practice, except that
SpamAssassin has rules that give messages with 78-byte lines spam points.
Mentioned by kjetilho on irc.
we add various information while analysing an incoming message. like
dkim/spf/ip reputation. and content-based junk filter threshold/result and
ham/spam words used.
for issue #179 by Fell and #157 by mattfbacon
