diff --git a/docker-compose.prod.yml b/docker-compose.prod.yml
index 4a32f5d2..3021235a 100644
--- a/docker-compose.prod.yml
+++ b/docker-compose.prod.yml
@@ -6,7 +6,7 @@ services:
     # Staging: relay to Mailpit (no authentication required)
     environment:
       - RELAYHOST=mailpit:1025
-      - ALLOWED_SENDER_DOMAINS=*
+      - ALLOWED_SENDER_DOMAINS=cmctechnologies.com.au
       # --- Gmail SMTP relay settings (uncomment for production) ---
       # - RELAYHOST=smtp-relay.gmail.com
       # - RELAYHOST_PORT=587