@@ -426,6 +426,27 @@ setting the ``auto_tls`` option to ``false`` in the DSN::
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427427 This setting only works when the ``smtp:// `` protocol is used.
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429+ Binding to IPv4 or IPv6
430+ ~~~~~~~~~~~~~~~~~~~~~~~
431+
432+ ..deprecated ::7.3
433+
434+ The option to bind to IPv4 or IPv6 or a specific IP address was introduced in Symfony 7.3.
435+
436+ By default, the underlying SocketStream will bind to IPv4 or IPv6 depending on the available
437+ interfaces. By specifying the ``source_ip `` option, binding to either IPv4 or IPv6 can be enforced,
438+ or even to a specific address. To bind to IPv4, use::
439+
440+ $dsn = 'smtp://smtp.example.com?source_ip=0.0.0.0';
441+
442+ As per RFC2732, IPv6 addresses must be surrounded by square brackets. To bind to IPv6, use::
443+
444+ $dsn = 'smtp://smtp.example.com?source_ip=[::]';
445+
446+ ..note ::
447+
448+ This setting only works when the ``smtp:// `` protocol is used.
449+
429450Overriding default SMTP authenticators
430451~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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