Some cleanup and changes:

- Don't upgrade the docker-compose file. (Not in the scope of this feature)
- No need to use aliases. Docker already resolves to service names
- Use a fixed IP range, which stays clear of the network ranges used by Docker. (172.xx.0.0/16)

docs/compose/.env

@@ -21,9 +21,6 @@ SECRET_KEY=ChangeMeChangeMe
 BIND_ADDRESS4=127.0.0.1
 BIND_ADDRESS6=::1
 
-# Internal Docker network
-IPV4_NETWORK=172.22.1
-
 # Main mail domain
 DOMAIN=mailu.io