diff --git a/core/postfix/conf/main.cf b/core/postfix/conf/main.cf
index fa442abf..ea210129 100644
--- a/core/postfix/conf/main.cf
+++ b/core/postfix/conf/main.cf
@@ -88,8 +88,11 @@ smtpd_recipient_restrictions =
   reject_non_fqdn_sender,
   reject_unknown_sender_domain,
   reject_unknown_recipient_domain,
+  reject_unverified_recipient,
   permit
 
+unverified_recipient_reject_reason = Address lookup failure
+
 ###############
 # Milter
 ###############