diff --git a/README.md b/README.md
index 896fbb2..90898c0 100644
--- a/README.md
+++ b/README.md
@@ -34,6 +34,14 @@ Following Files are important and have been changed and setup with the script:
 * docker.config
 * docker-compose.yml
 
+## Add additional custom configs
+
+To add additional custom environment variables, you can add a file .env.custom and add your variables there.
+This file will not be changed from the setup script and will be used inside all containers to overwrite the existing .env and .env.local
+```sh
+MAILER_DSN='smtp://null'
+DEFAULT_LANGUAGE='de'
+```
 
 ## Final Result
 Following final Result should be printed from the docker-compose command: