Change incorrect message, when the sender in the global envelope or t…

…he from header of asEmailMessage() is not defined.

Channel/EmailChannel.php

@@ -57,7 +57,7 @@ public function notify(Notification $notification, RecipientInterface $recipient
         if ($email instanceof Email) {
             if (!$email->getFrom()) {
                 if (null === $this->from) {
-                    throw new LogicException(sprintf('To send the "%s" notification by email, you should either configure a global "from" header, set a sender in the global "envelope" of the mailer configuration or set a "from" header in the "asEmailMessage()" method.', get_debug_type($notification)));
+                    throw new LogicException(sprintf('To send the "%s" notification by email, you must configure the global "from" header. For this you can set a sender in the global "envelope" of the mailer configuration or set a "from" header in the "asEmailMessage()" method.', get_debug_type($notification)));
                 }
 
                 $email->from($this->from);