Add SMTP_USER, SMTP_PASSWORD from environment vars. (#599)

* add smtp user, password from environment

add smtp user, password from environment to mailman.cfg

* Update README.md

document SMTP authentication via docker-compose.yml

* Update README.md

* Create docker-compose-traefik.yml

real life example

* remove examples folder for later use

core/docker-entrypoint.sh

@@ -142,6 +142,8 @@ lmtp_host: $MM_HOSTNAME
 lmtp_port: 8024
 smtp_host: $SMTP_HOST
 smtp_port: $SMTP_PORT
+smtp_user: $SMTP_HOST_USER
+smtp_pass: $SMTP_HOST_PASSWORD
 configuration: python:mailman.config.exim4
 
 EOF
@@ -163,6 +165,8 @@ lmtp_host: $MM_HOSTNAME
 lmtp_port: 8024
 smtp_host: $SMTP_HOST
 smtp_port: $SMTP_PORT
+smtp_user: $SMTP_HOST_USER
+smtp_pass: $SMTP_HOST_PASSWORD
 configuration: /etc/postfix-mailman.cfg
 
 EOF