Заставить cron не мылить мне ежеминутные отчеты на root@localhost?

00 21 * * * some_command &>/dev/null

и тишина ...

man 5 crontab

In addition to LOGNAME, HOME, and SHELL, cron(8) will look at MAILTO if
     it has any reason to send mail as a result of running commands in
     ``this'' crontab.  If MAILTO is defined (and non-empty), mail is sent to
     the user so named.  MAILTO may also be used to direct mail to multiple
     recipients by seperating recipient users with a comma.  If MAILTO is
     defined but empty (MAILTO=""), no mail will be sent.  Otherwise mail is
     sent to the owner of the crontab.  This option is useful if you decide on
     /bin/mail instead of /usr/lib/sendmail as your mailer when you install
     cron -- /bin/mail doesn't do aliasing, and UUCP usually doesn't read its
     mail.

этот вариант хорош, если товарищ для выполнения своих задач использует личный crontab ($ crontab -e) В противном случае он вообще не будет получать системных сообщений