await mailofly.emails.send({
  from: "support@yourdomain.com",
  to: ["customer@example.com"],
  subject: "Ticket #4082 Update",
  html: "<p>We have updated your support ticket.</p>",
  headers: {
    "X-Entity-Ref-ID": "ticket_4082",
    "In-Reply-To": "<msg_original_id@yourdomain.com>",
    "References": "<msg_original_id@yourdomain.com>"
  }
});