如何将表单数据提交到Fancybox中的外部URL？

I have a form like this;

我有这样的表格;

<form action="https://www.exampleurl.com" method="post" id="postForm">
    @Html.HiddenFor(x => x.hiddenField)
    <button type="submit" id="btnSubmit">Submit</button>
</form>
<form act