diff --git a/smtp.mail.inc b/smtp.mail.inc
index 53bf317..1313af4 100644
--- a/smtp.mail.inc
+++ b/smtp.mail.inc
@@ -467,7 +467,7 @@ class SmtpMailSystem implements MailSystemInterface {
               }
 
               $attachment_new_filename = drupal_tempnam('temporary://', 'smtp');
-              $file_path = file_save_data($attachment, $attachment_new_filename, FILE_EXISTS_REPLACE);
+              $file_path = file_unmanaged_save_data($attachment, $attachment_new_filename, FILE_EXISTS_REPLACE);
               $real_path = drupal_realpath($file_path->uri);
 
               if (!$mailer->AddAttachment($real_path, $file_name)) {