diff --git a/README.md b/README.md
index 3ca5ffc..e8f6267 100644
--- a/README.md
+++ b/README.md
@@ -83,6 +83,12 @@ cd docker
    echo 'MAIL_DOMAIN=chat.example.org' > .env
    ```
 
+   Optionally add a contact address for Let's Encrypt renewal notices:
+
+   ```bash
+   echo 'ACME_EMAIL=admin@example.org' >> .env
+   ```
+
    The container generates a `chatmail.ini` with defaults from `MAIL_DOMAIN` on first start.
    To customize chatmail settings, mount your own `chatmail.ini` instead
    (see [Custom chatmail.ini](#custom-chatmailiini) below).
diff --git a/docker-compose.yaml b/docker-compose.yaml
index ad0a01c..ecf9a9d 100644
--- a/docker-compose.yaml
+++ b/docker-compose.yaml
@@ -39,6 +39,7 @@ services:
         max-file: "3"
     environment:
       MAIL_DOMAIN: $MAIL_DOMAIN
+      ACME_EMAIL: ${ACME_EMAIL:-}
     network_mode: "host"
     volumes:
       ## system (required)
diff --git a/env.example b/env.example
index 3eebb37..1c7c227 100644
--- a/env.example
+++ b/env.example
@@ -1 +1,2 @@
 MAIL_DOMAIN=chat.example.com
+# ACME_EMAIL=admin@example.com
diff --git a/scripts/chatmail-init.sh b/scripts/chatmail-init.sh
index fc1015a..9b33578 100755
--- a/scripts/chatmail-init.sh
+++ b/scripts/chatmail-init.sh
@@ -41,6 +41,13 @@ if [ -n "${TLS_EXTERNAL_CERT_AND_KEY:-}" ]; then
     fi
 fi
 
+# Inject ACME contact email from env var unless defined in chatmail.ini.
+if [ -n "${ACME_EMAIL:-}" ]; then
+    if ! grep -q '^acme_email' "$CHATMAIL_INI"; then
+        echo "acme_email = $ACME_EMAIL" >> "$CHATMAIL_INI"
+    fi
+fi
+
 # Ensure mailboxes directory exists (chatmail-metadata needs it at startup,
 # but Dovecot only creates it on first mail delivery)
 mkdir -p "/home/vmail/mail/${MAIL_DOMAIN}"