diff --git a/services/mailer/mailer.go b/services/mailer/mailer.go
index cc0ad0454d..bf4b5a43cb 100644
--- a/services/mailer/mailer.go
+++ b/services/mailer/mailer.go
@@ -1,5 +1,6 @@
 // Copyright 2014 The Gogs Authors. All rights reserved.
 // Copyright 2017 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
 
 package mailer