Postfix docker
https://hub.docker.com/r/boky/postfix/
https://github.com/jeremybusk/docker-postfix
Alternatives
https://github.com/mail-in-a-box/mailinabox
https://github.com/eldada/postfix-relay-kubernetes
https://github.com/catatnight/docker-postfix
https://github.com/juanluisbaptiste/docker-postfix best?
https://github.com/jessfraz/dockerfiles/tree/master/postfix
https://github.com/noteed/docker-postfix/blob/master/Dockerfile
https://github.com/alterrebe/docker-mail-relay
https://upcloud.com/resources/tutorials/secure-postfix-using-lets-encrypt
https://ubuntu.com/server/docs/mail-postfix#:~:text=SMTP%20Authentication
https://help.ubuntu.com/community/PostfixDovecotSASL
https://wiki.debian.org/PostfixAndSASL
https://github.com/humpedli/docker-postfix-dovecot
https://doc.dovecot.org/configuration_manual/howto/postfix_and_dovecot_sasl/