Merge #3120

3120: Update the traefik doc r=mergify[bot] a=nextgens

## What type of PR?

documentation

## What does this PR do?

Update the traefik doc

### Related issue(s)
- #2903
- #3052 

## Prerequisites
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.

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


Co-authored-by: Florent Daigniere <nextgens@freenetproject.org>

docs/reverse.rst

@@ -12,13 +12,14 @@ Web contents based on criteria like the requested hostname (virtual hosts).
 Traefik as reverse proxy
 ------------------------
 
-In your docker-compose.yml, add a section like follows:
+In your docker-compose.yml, remove the `ports` section of the `front` container
+and add a section like follows:
 
 .. code-block:: yaml
 
   reverse-proxy:
     # The official v2 Traefik docker image
-    image: traefik:v2.10
+    image: traefik:v2.11
     # Enables the web UI and tells Traefik to listen to docker
     command:
       - "--providers.docker=true"
@@ -34,10 +35,9 @@ In your docker-compose.yml, add a section like follows:
       - "--entrypoints.pop3.address=:pop3"
       - "--entrypoints.pop3s.address=:pop3s"
       - "--entrypoints.sieve.address=:sieve"
-        #  - "--api.insecure=true"
-      - "--log.level=DEBUG"
+      # - "--api.insecure=true"
+      # - "--log.level=DEBUG"
     ports:
-      # The HTTP port
       - "25:25"
       - "80:80"
       - "443:443"
@@ -49,7 +49,7 @@ In your docker-compose.yml, add a section like follows:
       - "143:143"
       - "4190:4190"
       # The Web UI (enabled by --api.insecure=true)
-      #- "8080:8080"
+      # - "8080:8080"
     volumes:
       # So that Traefik can listen to the Docker events
       - /var/run/docker.sock:/var/run/docker.sock
@@ -61,12 +61,12 @@ and then add the following to the front section:
   labels:
       - "traefik.enable=true"
 
-      # the second part is important to ensure Mailu can get certificates from letsencrypt
-      - "traefik.http.routers.web.rule=Host(`mail.example.com`) || Path(`/.well-known/acme-challenge/`)"
+      # the second part is important to ensure Mailu can get certificates from letsencrypt for all hostnames
+      - "traefik.http.routers.web.rule=Host(`mail.example.com`) || PathPrefix(`/.well-known/acme-challenge/`)"
       - "traefik.http.routers.web.entrypoints=web"
       - "traefik.http.services.web.loadbalancer.server.port=80"
 
-      #other FQDNS can be added here:
+      # other FQDNS can be added here:
       - "traefik.tcp.routers.websecure.rule=HostSNI(`mail.example.com`) || HostSNI(`autoconfig.example.com`) || HostSNI(`mta-sts.example.com`)"
       - "traefik.tcp.routers.websecure.entrypoints=websecure"
       - "traefik.tcp.routers.websecure.tls.passthrough=true"