[10.x] Return response from mail notification channel

[xalaida]

What is the problem?

Currently, there is no way to read the response from the mail notification channel because the MailChannel does not return the mailer response.

This response is utilized by the NotificationSender on line 148:

$response = $this->manager->driver($channel)->send($notifiable, $notification);

$this->events->dispatch(
    new NotificationSent($notifiable, $notification, $channel, $response)
);

Thus, when listening to the NotificationSent event, the response property is always null.

This issue only occurs with the mail channel. Other default channels like broadcast or database work correctly.