diff --git a/lib/gitlab/email/receiver.rb b/lib/gitlab/email/receiver.rb
index 50c16da4ef6337e9458190bc83c9b4789eb51957..5f85f7ad03fe33d423af33314b1f8b36ea99c341 100644
--- a/lib/gitlab/email/receiver.rb
+++ b/lib/gitlab/email/receiver.rb
@@ -158,9 +158,7 @@ module Gitlab
       end
 
       def sent_notification
-        return nil unless reply_key
-
-        SentNotification.for(reply_key)
+        @sent_notification ||= SentNotification.for(reply_key) if reply_key
       end
 
       def add_attachments(reply, project)