hi, i'm not understanding this error message from the root admin, everything if working well but i keep receiving this email, the majoring of the zimbra config is default there are no cron jobs i configured

HTML Code:
Cron <root@mail> test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily )

/etc/cron.daily/logrotate:
error: error accessing /var/log/upstart: No such file or directory
error: upstart:1 glob failed for /var/log/upstart/*.log
error: found error in /var/log/upstart/*.log , skipping
Thanks