diff --git a/postfix/conf/main.cf b/postfix/conf/main.cf
index 09391e21..f43f2531 100644
--- a/postfix/conf/main.cf
+++ b/postfix/conf/main.cf
@@ -105,6 +105,7 @@ smtpd_sender_restrictions =
    permit_mynetworks,
    reject_non_fqdn_sender,
    reject_unknown_sender_domain,
+   reject_unlisted_sender,
    reject_sender_login_mismatch,
    permit