Running Ubuntu 13.04 for my server. In my mail server log I'm seeing the following message every week:

Dropped: root@admin → root@admin 'Cron <root@development> test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly )' No MX for [admin]
That being said, I have no idea where this cron job is coming from that is generating an email message. Where can I look to track this down and ultimately put a stop to it?