diff --git a/docker-compose.prod.yml b/docker-compose.prod.yml
index abf5c6eb..40ee1ccb 100644
--- a/docker-compose.prod.yml
+++ b/docker-compose.prod.yml
@@ -5,8 +5,7 @@ services:
     container_name: cmc-prod-postfix
     # Staging: relay to Mailpit (no authentication required)
     environment:
-      - RELAYHOST=mailpit
-      - RELAYHOST_PORT=1025
+      - RELAYHOST=mailpit:1025
       - ALLOWED_SENDER_DOMAINS=*
       # --- Gmail SMTP relay settings (uncomment for production) ---
       # - RELAYHOST=smtp-relay.gmail.com
diff --git a/docker-compose.stg.yml b/docker-compose.stg.yml
index 9c8ce597..e49b951a 100644
--- a/docker-compose.stg.yml
+++ b/docker-compose.stg.yml
@@ -5,8 +5,7 @@ services:
     container_name: cmc-stg-postfix
     # Staging: relay to Mailpit (no authentication required)
     environment:
-      - RELAYHOST=mailpit
-      - RELAYHOST_PORT=1025
+      - RELAYHOST=mailpit:1025
       - ALLOWED_SENDER_DOMAINS=cmctechnologies.com.au
       # --- Gmail SMTP relay settings (uncomment for production) ---
       # - RELAYHOST=smtp-relay.gmail.com