diff --git a/config/filter.d/courier-smtp.conf b/config/filter.d/courier-smtp.conf
index 2b9a13f2..7a3b9895 100644
--- a/config/filter.d/courier-smtp.conf
+++ b/config/filter.d/courier-smtp.conf
@@ -12,7 +12,8 @@ before = common.conf
 
 _daemon = courieresmtpd
 
-failregex = ^%(__prefix_line)serror,relay=<HOST>,.*: 550 User unknown\.$
+failregex = ^%(__prefix_line)serror,relay=<HOST>,.*: 550 User (<.*> )?unknown(\.)?$
+            ^%(__prefix_line)serror,relay=<HOST>,msg="535 Authentication failed\.",cmd: (AUTH PLAIN )?[0-9a-zA-Z\+/=]+$
 
 ignoreregex =