Delete all root mail / inbox on Linux / Unix from a shell prompt

Originally published at: https://www.cyberciti.biz/faq/delete-all-root-email-mailbox/

I have CentOS Linux acting as a router for our small community-based college. I see logwatch and other cron job generating emails for the root account. How do I delete those emails? I don’t want to disable email facility but just wanted to get rid of all root emails. How do I delete root user mails (mailbox) file in Linux or Unix like system?