diff --git a/main.go b/main.go
index 0eb563b..823fabc 100644
--- a/main.go
+++ b/main.go
@@ -234,7 +234,7 @@ func mailHandler(peer smtpd.Peer, env smtpd.Envelope) error {
 					"err_msg":  err.Msg,
 				}).Error("delivery failed")
 			default:
-				smtpError = smtpd.Error{Code: 554, Message: "Forwarding failed"}
+				smtpError = smtpd.Error{Code: 421, Message: "Forwarding failed"}
 
 				logger.WithError(err).
 					Error("delivery failed")