diff --git a/auth_test.go b/auth_test.go
index 984dbd6..fcb017e 100644
--- a/auth_test.go
+++ b/auth_test.go
@@ -1,3 +1,7 @@
+// SPDX-FileCopyrightText: 2024 The go-mail Authors
+//
+// SPDX-License-Identifier: MIT
+
 package mail
 
 import "testing"