diff --git a/README.md b/README.md
index 1f330c4..3b28292 100644
--- a/README.md
+++ b/README.md
@@ -37,7 +37,7 @@ git clone https://git.nemunai.re/happyDomain/happyDeliver.git
 cd happydeliver
 
 # Edit docker-compose.yml to set your domain
-# Change HAPPYDELIVER_DOMAIN and HOSTNAME environment variables
+# Change HAPPYDELIVER_DOMAIN environment variable and hostname
 
 # Build and start
 docker-compose up -d
@@ -63,7 +63,7 @@ docker run -d \
   -p 25:25 \
   -p 8080:8080 \
   -e HAPPYDELIVER_DOMAIN=yourdomain.com \
-  -e HOSTNAME=mail.yourdomain.com \
+  --hostname mail.yourdomain.com \
   -v $(pwd)/data:/var/lib/happydeliver \
   -v $(pwd)/logs:/var/log/happydeliver \
   happydeliver:latest
@@ -94,9 +94,9 @@ docker run -d \
   -p 25:25 \
   -p 8080:8080 \
   -e HAPPYDELIVER_DOMAIN=yourdomain.com \
-  -e HOSTNAME=mail.yourdomain.com \
   -e POSTFIX_CERT_FILE=/etc/ssl/certs/mail.yourdomain.com.crt \
   -e POSTFIX_KEY_FILE=/etc/ssl/private/mail.yourdomain.com.key \
+  --hostname mail.yourdomain.com \
   -v /path/to/your/certificate.crt:/etc/ssl/certs/mail.yourdomain.com.crt:ro \
   -v /path/to/your/private.key:/etc/ssl/private/mail.yourdomain.com.key:ro \
   -v $(pwd)/data:/var/lib/happydeliver \
diff --git a/docker-compose.yml b/docker-compose.yml
index fa27c5c..ccfd313 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -5,12 +5,12 @@ services:
       dockerfile: Dockerfile
     image: happydomain/happydeliver:latest
     container_name: happydeliver
+    # Set a hostname
     hostname: mail.happydeliver.local
 
     environment:
-      # Set your domain and hostname
-      DOMAIN: happydeliver.local
-      HOSTNAME: mail.happydeliver.local
+      # Set your domain
+      HAPPYDELIVER_DOMAIN: happydeliver.local
 
     ports:
       # SMTP port
diff --git a/docker/README.md b/docker/README.md
index 45cce6b..3769365 100644
--- a/docker/README.md
+++ b/docker/README.md
@@ -109,12 +109,13 @@ Default configuration for the Docker environment:
 
 The container accepts these environment variables:
 
-- `DOMAIN`: Email domain for test addresses (default: happydeliver.local)
-- `HOSTNAME`: Container hostname (default: mail.happydeliver.local)
+- `HAPPYDELIVER_DOMAIN`: Email domain for test addresses (default: happydeliver.local)
+
+Note that the hostname of the container is used to filter the authentication tests results.
 
 Example:
 ```bash
-docker run -e DOMAIN=example.com -e HOSTNAME=mail.example.com ...
+docker run -e HAPPYDELIVER_DOMAIN=example.com --hostname mail.example.com ...
 ```
 
 ## Volumes
diff --git a/docker/entrypoint.sh b/docker/entrypoint.sh
index bfe6088..1bc3eff 100644
--- a/docker/entrypoint.sh
+++ b/docker/entrypoint.sh
@@ -4,7 +4,7 @@ set -e
 echo "Starting happyDeliver container..."
 
 # Get environment variables with defaults
-HOSTNAME="${HOSTNAME:-mail.happydeliver.local}"
+[ -n "${HOSTNAME}" ] || HOSTNAME=$(hostname)
 HAPPYDELIVER_DOMAIN="${HAPPYDELIVER_DOMAIN:-happydeliver.local}"
 
 echo "Hostname: $HOSTNAME"