Merge #1684

1684: add warning about removing front r=mergify[bot] a=lub

## What type of PR?

documentation

## What does this PR do?

### Related issue(s)
- caused confusion e.g. in #1678

## Prerequistes
Before we can consider review and merge, please make sure the following list is done and checked.
If an entry in not applicable, you can check it or remove it from the list.

- [x] In case of feature or enhancement: documentation updated accordingly
- [ ] ~~Unless it's docs or a minor change: add [changelog](https://mailu.io/master/contributors/guide.html#changelog) entry file.~~


Co-authored-by: lub <git@lubiland.de>

docs/reverse.rst

@@ -225,6 +225,6 @@ You can also download the example configuration files:
 Disable completely Mailu reverse proxy
 --------------------------------------
 
-You can simply disable Mailu reverse proxy by removing the ``front`` section from the ``docker-compose.yml`` and use your own means to reverse proxy requests to the proper containers.
+You must not disable Mailu reverse proxy by removing the ``front`` section from the ``docker-compose.yml``.
 
-Be careful with this method as resolving container addresses outside the Docker Compose structure is a tricky task: there is no guarantee that addresses will remain after a restart and you are almost certain that addresses will change after every upgrade (and whenever containers are recreated).
+``front`` is handling authentication and is also proxying e.g. SMTP and IMAP. A basic HTTP reverse proxy as described in this document is not sufficient for this.