minor #15557 [Mailer] ping_threshold for ses+smtp (Tyraelqp)

This PR was squashed before being merged into the 5.4 branch.

Discussion
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[Mailer] ping_threshold for ses+smtp

Docs for symfony/symfony#42219

Commits
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7f54a27 [Mailer] ping_threshold for ses+smtp

Author: javiereguiluz

mailer.rst

@@ -174,6 +174,17 @@ party provider:
     For example, the DSN ``ses+smtp://ABC1234:abc+12/345@default`` should be
     configured as ``ses+smtp://ABC1234:abc%2B12%2F345@default``
 
+.. caution::
+
+    If you want to use ``ses+smtp`` transport together with :doc:`Messenger </messenger>`
+    to :ref:`send messages in background <mailer-sending-messages-async>`,
+    you need to add ``ping_threshold`` parameter to your ``MAILER_DSN`` with
+    value lower than ``10``: ``ses+smtp://USERNAME:PASSWORD@default?ping_threshold=9``
+
+    .. versionadded:: 5.4
+        
+        The ``ping_threshold`` option for ``ses-smtp`` was introduced in Symfony 5.4.
+
 .. note::
 
     When using SMTP, the default timeout for sending a message before throwing an
@@ -1112,6 +1123,8 @@ the final email)::
     $email->getHeaders()->addTextHeader('X-Transport', 'alternative');
     $mailer->send($email);
 
+.. _mailer-sending-messages-async:
+
 Sending Messages Async
 ----------------------