Move the configuration file to .env to support global variables

.env

@@ -0,0 +1,36 @@
+# Freeposte.io main configuration file
+#
+# Most configuration variables can be modified through the Web interface,
+# these few settings must however be configured before starting the mail
+# server and require a restart upon change.
+
+# Project name
+COMPOSE_PROJECT_NAME=freeposte
+
+# Set this to the path where Freeposte data and configuration is stored
+ROOT=/freeposte
+
+# Set this to enable debugging globally
+DEBUG=False
+
+# Set to a randomly generated 16 bytes string
+SECRET_KEY=ChangeMeChangeMe
+
+# Main mail domain
+DOMAIN=freeposte.io
+
+# Exposed mail-server hostname
+HOSTNAME=mail.freeposte.io
+
+# Postmaster local part (will append the main mail domain)
+POSTMASTER=admin
+
+# Networks granted relay permissions, make sure that you include your Docker
+# internal network (default to 172.17.0.0/16)
+RELAYNETS=172.16.0.0/12
+
+# Will relay all outgoing mails if configured
+RELAYHOST=
+
+# Fetchmail delay
+FETCHMAIL_DELAY=600