It is unlikely to be genuine corruption, but more like the effects of two mutually incompatble mail user agents.Some of the things mail user agents do are described here.
Emacs - rmail writes message separators into the mail file. IGrep the mailbox for 'BABYL' The following command will rectify things:
# sed -e '1,6d' -e '/^V^_^V^L/d' -e '/0, unseen,,/d' -e '/\*\*\* EOOH
\*\*\*/d' \
-e 's/Mail-from: //' < /var/mail/mailfile > /tmp/newmailfile
$Header$
@