diff --git a/51-filter-postfix-aggregate.conf b/51-filter-postfix-aggregate.conf
index 0a6cd03..3b2492e 100644
--- a/51-filter-postfix-aggregate.conf
+++ b/51-filter-postfix-aggregate.conf
@@ -2,7 +2,9 @@ filter {
   if ![postfix_queueid] {
     drop {}
   } else if [postfix_queueid] == "NOQUEUE" {
-    drop {}
+    # Ignore events where the queueid is NOQUEUE, they can't be aggregated.
+    # The empty mutate filter serves as a 'noop',
+    mutate {}
   } else if [program] == "postfix/qmgr" and [postfix_from] {
     aggregate {
       task_id => "%{postfix_queueid}"