diff --git a/Using-in-Kubernetes.md b/Using-in-Kubernetes.md
index ecd24ef..dc624c2 100644
--- a/Using-in-Kubernetes.md
+++ b/Using-in-Kubernetes.md
@@ -376,6 +376,7 @@ data:
   postfix-main.cf: |
     postscreen_upstream_proxy_protocol = haproxy
   postfix-master.cf: |
+    smtp/inet/postscreen_upstream_proxy_protocol=haproxy
     submission/inet/smtpd_upstream_proxy_protocol=haproxy
     smtps/inet/smtpd_upstream_proxy_protocol=haproxy
   dovecot.cf: |