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?
Is there anything in /etc/cron.weekly folder?
Yes, three files:
apt-security-updates
apt-xapian-index
man-db
However, when I edit the crontab (sudo crontab -e) there are no cron jobs listed. Could one of these files be causing the email message I’m seeing?
If you can’t tell, server administration is not my strong point. 
Cannot say exactly, cause I don’t use Ubuntu and don’t know what inside those cron files. However, you can check their content and compare with the above log to find out.