diff --git a/helper/mailgun.api.php b/helper/mailgun.api.php
new file mode 100644
index 0000000..5dc342a
--- /dev/null
+++ b/helper/mailgun.api.php
@@ -0,0 +1,14 @@
+<?php
+/**
+ * @file mailgun.api.php
+ * @date 2019-04-12
+ * @author Go Namhyeon <gnh1201@gmail.com>
+ * @brief Mailgun REST API interface module
+ * @documentation https://documentation.mailgun.com/en/latest/api-sending.html
+ */
+
+if(!check_function_exists("mailgun_send_message")) {
+  function mailgun_send_message() {
+    // todo
+  }
+}