Merge branch '4.2' into 4.3

* 4.2:
  Uncomment code and add info

Author: javiereguiluz

email.rst

@@ -78,16 +78,15 @@ sending an email is pretty straightforward::
                 ),
                 'text/html'
             )
-            /*
-             * If you also want to include a plaintext version of the message
+
+            // you can remove the following code if you don't define a text version for your emails
             ->addPart(
                 $this->renderView(
                     'emails/registration.txt.twig',
                     ['name' => $name]
                 ),
                 'text/plain'
             )
-            */
         ;
 
         $mailer->send($message);