vi /etc/postfix/main.cf remove the domain 1... 2... 3#mydestination = example.com, localhost.com, localhost 4mydestination = localhost 5... 6... Then restart postfix: 1/etc/init.d/postix restart See some further discussion in https://www.digitalocean.com/community/questions/why-won-t-postfix-deliver-mail-to-own-domain