tip to not follow redirects when testing mailer

Author: dbu

mailer.rst

@@ -1597,6 +1597,11 @@ the :class:`Symfony\\Bundle\\FrameworkBundle\\Test\\MailerAssertionsTrait`::
         }
     }
 
+.. tip::
+
+   If your controller returns a redirect response after sending the email, make sure to have your client *not* follow redirects.
+   The kernel is rebooted after following the redirection and the message lost from the mailer event handler.
+
 .. _`Amazon SES`: https://github.com/symfony/symfony/blob/{version}/src/Symfony/Component/Mailer/Bridge/Amazon/README.md
 .. _`App Password`: https://support.google.com/accounts/answer/185833
 .. _`default_socket_timeout`: https://www.php.net/manual/en/filesystem.configuration.php#ini.default-socket-timeout