On a server running Zimbra on Ubuntu, to get cron job output sent to an e-mail address, make the following link:
ln -s /opt/zimbra/postfix/sbin/sendmail /usr/sbin/sendmail
Until this is done, crontab output will silently vaporize.
Installing the mta-dummy and mailx packages, then adding
set sendmail=/opt/zimbra/postfix/sbin/sendmail
to /etc/mail.rc will allow the
mail
command to send correctly, but will not enable crontab messages. I was under the false assumption that cron used the mail/mailx command when sending cron mail. This is an option, but whether to use mail/mailx or sendmail directly is a compile-time option, with most Linux distributions choosing to use /usr/sbin/sendmail directly.