Few improvements

[sashkab]

some advise:

• do not use multi-instance setup -> use multiple container
• make $(postconf data_directory) and $(postconf queue_directory) persistent volumes, separate per container
• $(postconf config_directory) could be mounted read only
• docker healthcheck can be used to monitor the number of items in a deferred queue
• "postfix reload" works

-> works, give it a try :-)

via http://postfix.1071664.n5.nabble.com/Is-it-possible-to-run-postfix-in-a-container-e-g-docker-red-hot-tp102393p102399.html