minor #15406 Adding missing ntlm authentication mode to SwiftmailerBundle config (jbonnier)

This PR was merged into the 4.4 branch.

Discussion
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Adding missing ntlm authentication mode to SwiftmailerBundle config

Hey guys!

The NTLM auth mode seems to be missing in the config docs for SwiftmailerBundle.

Added with PR [188](symfony/swiftmailer-bundle#188)

Cheers!

Commits
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4fd0bce Adding missing ntlm authentication mode to SwiftmailerBundle configuration

Author: javiereguiluz

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
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