diff --git a/apps/base/mail/stalwart-statefulset.yaml b/apps/base/mail/stalwart-statefulset.yaml
index f0ec3a1..964b105 100644
--- a/apps/base/mail/stalwart-statefulset.yaml
+++ b/apps/base/mail/stalwart-statefulset.yaml
@@ -21,6 +21,7 @@ spec:
     metadata:
       labels:
         app.kubernetes.io/name: stalwart
+        mail.unkin.net/smarthost-client: "true"
     spec:
       securityContext:
         runAsNonRoot: true