***** INSTALLING POSTFIX ON DEBIAN/UBUNTU ***** ********* Part 1 ************* Require HELO as per RFC $sudo sh -c "echo smtpd_helo_required = yes >> /etc/postfix/main.cf" $sudo service postfix restart Try From the Server, telnet localhost port 25 $telnet localhost 25 Then type the following pressing enter after each line: mail from: manager@theGrandLottery.com You should be prompted to require HELO first ************* Part 2 *************** Sending email to the world sudo sh -c "echo inet_protocols = ipv4 >> /etc/postfix/main.cf" echo "This is my email, hello" | mail -s "This is a test message" yyy@gmail.com