diff --git a/reference/configuration/swiftmailer.rst b/reference/configuration/swiftmailer.rst
index 674cee6ae53..3c04762274e 100644
--- a/reference/configuration/swiftmailer.rst
+++ b/reference/configuration/swiftmailer.rst
@@ -152,7 +152,11 @@ auth_mode
 **type**: ``string``
 
 The authentication mode to use when using ``smtp`` as the transport. Valid
-values are ``plain``, ``login``, ``cram-md5``, or ``null``.
+values are ``plain``, ``login``, ``cram-md5``,, ``ntlm`` or ``null``.
+
+.. versionadded:: 3.0.4
+
+    The ``ntlm`` authentication mode was introduced in SwiftMailerBundle 3.0.4.
 
 spool
 ~~~~~