diff --git a/rootfs/etc/confd/templates/main.cf.tmpl b/rootfs/etc/confd/templates/main.cf.tmpl
index f5cfb19..6cbc15a 100644
--- a/rootfs/etc/confd/templates/main.cf.tmpl
+++ b/rootfs/etc/confd/templates/main.cf.tmpl
@@ -6,6 +6,8 @@ mydomain = {{getenv "MYDOMAIN"}}
 myorigin = $mydomain
 mydestination = $myhostname, localhost
 
+proxy_interfaces = {{getenv "EXTERNAL_IP"}}
+
 unknown_local_recipient_reject_code = 550
 mynetworks_style = host
 relay_domains = $mydestination