we've been having problems with nulls showing
up in email.  it turns out that the dot destuffing
in smtpd is the culprit.  i also added some extra
paranoid stuff to the getnl() stuff to make the
sender isn't messing with us.  to trigger this bug
send a mail with a dot on a line by itself. (or
telnet to smtpd and forge the email yourself,
this time doing the dot-stuffing by hand.)