I installed postfix following this tutorial. https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-postfix-as-a-send-only-smtp-server-on-debian-9 including edit postfix/conf.cf line myhostname = e-usine.com and still recive emails as @ubuntu-s-1vcpu-1gb-lon1-01
These answers are provided by our Community. If you find them useful, show some love by clicking the heart. If you run into issues leave a comment, or add your own answer to help others.