Docker Development questions/issues/documentation

We are attempting to install a docker developer environment on ubuntu following the documentation here:

When we reach the step to start docker we are confused about what the ESN_HOST variable should be.
Should it be the i.p. address of our local machine ?
Should it be the ip address of the domain name that we are testing OpenPass on (https://example.com)
In our openpaas-esn directory and in /docker/dockerfiles/dev/ the Docker-Compose.yml has the DOCKER_IP variable set to “localhost”.
Is this the correct setting for this variable ?
Should it be the i.p. address of our local machine ?
Should it the ip address of the domain name that we are testing OpenPass on (https://example.com)
Is there any documentation on how the portal admin can configure the James server so that users can both send and receive emails within the unified inbox ?
Is there any documentation on how to configure the JMAP settings as the portal admin ?
Is there any documentation on how to configure the DAV server settings as the portal admin?
Thanks !

I dont know about ubuntu… but check out the copy james config section

cp /usr/share/openpaas/packaging/common/openpaas-james/package/etc/james/* /var/lib/james/conf/