I guess it's something like https://github.com/docker-library/official-images/tree/master/library https://github.com/docker-library/official-images/blob/master/library/postfixadmin
I guess it's something like
https://github.com/docker-library/official-images/tree/master/library
https://github.com/docker-library/official-images/blob/master/library/postfixadmin