Getting notified of failed cron jobs

You could redirect the error output of your cronjob command to a file. Here is an example of a line in /etc/crontab:

01 3    * * *   user    /bin/command 2>> /var/log/some.file

Then at least you got a clue if errors occured. You might even write a script to notify you over notify-osd or similar tools when the file changes.

Edit:

The file /var/log/syslog reports messages from cron as well. You might want to take a look at that. To get a dedicated log-file for the cron deamon edit /etc/rsyslog.d/50-default.conf and uncomment/edit the line that says:

#cron.*             /var/log/cron.log

Don't know what you'll find there but worth the try. Report how it went.