The Cron Email setting controls where cPanel sends cron output notifications.
Enter an email address and save it to receive cron output. To stop all cron mail, remove the address. cPanel also documents redirecting a specific command's output to /dev/null 2>&1 when you intentionally want to suppress that job's output.
Do not suppress errors merely to make notifications disappear. Verify that the scheduled task completes successfully before discarding its output.