Flarum\Core\Listener\EmailConfirmationMailer::whenUserWasRegistered PHP Method

    public function whenUserWasRegistered(UserWasRegistered $event)
    {
        $user = $event->user;
        if ($user->is_activated) {
            return;
        }
        $data = $this->getEmailData($user, $user->email);
        $body = $this->translator->trans('core.email.activate_account.body', $data);
        $this->mailer->raw($body, function (Message $message) use($user, $data) {
            $message->to($user->email);
            $message->subject('[' . $data['{forum}'] . '] ' . $this->translator->trans('core.email.activate_account.subject'));
        });
    }