Cron root@localhost test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily )

/etc/cron.daily/pam_shield:
logging debug info
allowing from localhost
allowing from 127.0.0.1/255.0.0.0
done reading config file, 0 errors
expiring entry
expiring entry
expiring entry
expiring entry
expiring entry
expiring entry
expiring entry
expiring entry
expiring entry
expiring entry
expiring entry
expiring entry
expiring entry
expiring entry
expiring entry
expiring entry
expiring entry
expiring entry
storing updated entry
expiring entry
expiring entry
expiring entry

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こんな感じでログが毎日メールされてきてる。
エラーの時だけ送信して欲しいんだけど、どうすればいいん？