recommend stalwart mail server in aio

Signed-off-by: Simon L <szaimen@e.mail.de>

readme.md

@@ -707,7 +707,7 @@ If you want to use the user_sql app, the easiest way is to create an additional
 It is possible to install any of these to get a GUI for your AIO database. The pgAdmin container is recommended. You can get some docs on it here: https://www.pgadmin.org/docs/pgadmin4/latest/container_deployment.html. For the container to connect to the aio-database, you need to connect the container to the docker network `nextcloud-aio` and use `nextcloud-aio-database` as database host, `oc_nextcloud` as database username and the password that you get when running `sudo docker exec nextcloud-aio-nextcloud grep dbpassword config/config.php` as the password. Apart from that there is now a way for the community to add containers: https://github.com/nextcloud/all-in-one/discussions/3061#discussioncomment-7307045
 
 ### Mail server
-You can configure one yourself by using either of these three recommended projects: [Docker Mailserver](https://github.com/docker-mailserver/docker-mailserver/#docker-mailserver), [Mailu](https://github.com/Mailu/Mailu), [Maddy Mail Server](https://github.com/foxcpp/maddy#maddy-mail-server) or [Mailcow](https://github.com/mailcow/mailcow-dockerized#mailcow-dockerized-------). Docker Mailserver and Maddy Mail Server are probably a bit easier to set up as it is possible to run them using only one container but Mailcow and Mailu both have more features. Apart from that there is now a way for the community to add containers: https://github.com/nextcloud/all-in-one/discussions/356#discussioncomment-7133547
+You can configure one yourself by using either of these four recommended projects: [Docker Mailserver](https://github.com/docker-mailserver/docker-mailserver/#docker-mailserver), [Mailu](https://github.com/Mailu/Mailu), [Maddy Mail Server](https://github.com/foxcpp/maddy#maddy-mail-server), [Mailcow](https://github.com/mailcow/mailcow-dockerized#mailcow-dockerized-------) or [Stalwart](https://stalw.art/). There is now a community container which allows to easily add Stalwart Mail server to AIO: https://github.com/nextcloud/all-in-one/tree/main/community-containers/stalwart
 
 ### How to migrate from an already existing Nextcloud installation to Nextcloud AIO?
 Please see the following documentation on this: [migration.md](https://github.com/nextcloud/all-in-one/blob/main/migration.md)