Delete all root mail / inbox from a shell prompt

The easilst way is to empty root / users email message file i.e. /var/spool/mail/root or /var/spool/mail/username. Simply type the following command at shell:

> /var/spool/mail/root 

OR

cat /dev/null > /var/spool/mail/root 

OR

echo "" > /var/spool/mail/root