diff --git a/README.md b/README.md
index a3f3e47..579312e 100644
--- a/README.md
+++ b/README.md
@@ -33,3 +33,13 @@ Following Files are important and have been changed and setup with the script:
 * .env.local
 * 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'
+```
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