You can do following changes:

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>

<form action="https://formsubmit.co/[email protected]" method="POST" class="form">
    <input type="text" name="name" required>
    <input type="email" name="email" required>
    <button type="submit">Submit</button>
</form>

<script>
    $(document).ready(function(){
        $('.form').on('submit', function(){
            alert('Your details were successfully received.');
        });
    });
</script>

Typically I don't advocate for pop ups unless really necessary. However there are some exceptions. IF the button 'Contact Sales' appears as a persistent button, then it makes sense that you want to keep the user in the task flow or context they were in when they decided to 'Contact Sales'. So, if your user will access this button frequently, while performing a task then have them fill out the form in a pop up. That way then perform this sub-task in context of their workflow, but when done they can close the form (pop up) and not have to click back their point of origin or workflow context.