minor #7862 Backport #7510 for the Symfony 2.7 docs (mykiwi, javiereguiluz, xabbuh)

This PR was merged into the 2.7 branch.

Discussion
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Backport #7510 for the Symfony 2.7 docs

All the documented options are part of SwiftmailerBundle releases that are compatible with Symfony 2.7.

Commits
-------

1c39991 fix versionadded directives
8eaccef Removed "encryption" and "auth_mode" from the list of %env()% compatible options
3395258 Fixed ... again ... the versionadded directives
3333723 Added the missing "versionadded" directives
0e2853a add mail transport as deprecated
2bd1a22 Minor tweaks
b161bd8 update swiftmailer reference

Author: xabbuh

reference/configuration/swiftmailer.rst

@@ -18,11 +18,15 @@ a mailer. It is also possible to configure several mailers (see
 Configuration
 -------------
 
+* `url`_
 * `transport`_
 * `username`_
 * `password`_
 * `host`_
 * `port`_
+* `timeout`_
+* `source_ip`_
+* `local_domain`_
 * `encryption`_
 * `auth_mode`_
 * `spool`_
@@ -37,6 +41,15 @@ Configuration
 * `disable_delivery`_
 * `logging`_
 
+url
+~~~
+
+**type**: ``string``
+
+The entire SwiftMailer configuration using a DSN-like URL format.
+
+Example: ``smtp://user:pass@host:port/?timeout=60&encryption=ssl&auth_mode=login&...``
+
 transport
 ~~~~~~~~~
 
@@ -46,7 +59,7 @@ The exact transport method to use to deliver emails. Valid values are:
 
 * smtp
 * gmail (see :doc:`/email/gmail`)
-* mail
+* mail (deprecated in SwiftMailer since version 5.4.5)
 * sendmail
 * null (same as setting `disable_delivery`_ to ``true``)
 
@@ -79,6 +92,30 @@ port
 The port when using ``smtp`` as the transport. This defaults to 465 if encryption
 is ``ssl`` and 25 otherwise.
 
+timeout
+~~~~~~~
+
+**type**: ``integer``
+
+The timeout in seconds when using ``smtp`` as the transport.
+
+source_ip
+~~~~~~~~~
+
+**type**: ``string``
+
+The source IP address when using ``smtp`` as the transport.
+
+local_domain
+~~~~~~~~~~~~
+
+**type**: ``string``
+
+.. versionadded:: 2.4.0
+    The ``local_domain`` option was introduced in SwiftMailerBundle 2.4.0.
+
+The domain name to use in ``HELO`` command.
+
 encryption
 ~~~~~~~~~~
 
@@ -191,6 +228,13 @@ logging
 If true, Symfony's data collector will be activated for Swift Mailer and
 the information will be available in the profiler.
 
+.. tip::
+
+    The following options can be set via environment variables using the
+    ``%env()%`` syntax: ``url``, ``transport``, ``username``, ``password``,
+    ``host``, ``port``, ``timeout``, ``source_ip``, ``local_domain``.
+    For details, see the :doc:`/configuration/external_parameters` article.
+
 Full Default Configuration
 --------------------------