Edit the sudoer file using
# visudo
Enabled the sudo user and enter the following entry in bottom of the file
Defaults mailto = "alertforxxxxxx@gmail.com"
Defaults mailfrom = "root@xxxxxxx.com"
Defaults mail_badpass
Defaults mail_always
Defaults mail_no_user
Defaults mailsub = "*** Command run via sudo on %h ***"
Defaults badpass_message = "Please Provide Correct Password"
Defaults !lecture,tty_tickets,!fqdn,!syslog
Defaults logfile=/var/log/sudo.log
This will send email's while some user's use sudo command.