actuel-inactuel/site/config/routes/send-newsletter.php

<?php

return [
  'pattern' => '/send-newsletter.json',
  'method' => 'POST',
  'action'  => function () {
      $jsonRequest = file_get_contents("php://input");
      $request = json_decode($jsonRequest);

      $kirby = kirby();

      $emailPage = page($data->uri);
      $content = $emailPage->content()->kt();
      
      try {
            if ($kirby->email([
                'from'    => "info@actuel-inactuel.fr",
                'to'      => page("inscription")->toStructure()->pluck("email"),
                'subject' => $data->subject,
                'body'    => [
                  "html" => $emailPage->content()
                ],
            ])->isSent()) {
                return json_encode(['status' => 'success', 'message' => 'Email envoyé avec succès.']);
            } else {
                return json_encode([
                    "status" => "error",
                    "message" => "Erreur lors de l'envoi de l'email.",
                ]);
                
            }
      } catch (Exception $error) {
          return json_encode(['status' => 'error', 'message' => $error->getMessage()]);
      }
  }
];