If you have configured many cronjob’s to run every minute or so on, & also using Gmail as mail relay system on the same box, you might see following in /var/log/mail.log
Jun 8 10:21:10 radius postfix/smtp[5192]: 6DA0D16E0118: to=, relay=smtp.gmail.com[74.125.71.108]:587, delay=3.3, delays=0.01/0/2.9/0.41, dsn=5.4.5, status=bounced (host smtp.gmail.com[74.125.71.108] said: 550 5.4.5 Daily user sending quota exceeded. e188-v6sm2329623wmf.21 - gsmtp (in reply to DATA command))
CRON will only email you if there is some output from you job. With everything redirected to null, there is no output and hence cron will not email you.
Using > /dev/null 2>&1 will redirect all your command output (both stdout and stderr) to /dev/null, meaning no outputs are printed to terminal.
If you have configured an emailing system which is using gmail (which limits 500 messages per day) as mail relay then put the following command at the end of the cron job line that always output the result.
Example:
Before:
*/5 * * * * /temp/mybashscript.sh
After:
*/5 * * * * /temp/mybashscript.sh >/dev/null 2>&1
Regard’s
Syed Jahaznaib