Send email with headers (Prevents going to spam)

form.html

<form class="form-horizontal col-md-10 cform" id="cform">
    <div class="form-group">
        <label class="control-label">Name*</label>
        <input type="text" class="form-control" name="name" required />
    </div>
    <div class="form-group">
        <label class="control-label">E-mail Address*</label>
        <input type="email" class="form-control" name="email" required/>
    </div>
    <div class="form-group">
        <label class="control-label">Subject*</label>
        <input type="text" class="form-control" name="subject" required/>
    </div>
    <div class="form-group">
        <label class="control-label">Message*</label>
        <textarea col="10" rows="5" class="form-control" name="message" required></textarea>
    </div>
    <div class="form-group">
        <button type="submit" class="btn btn-success">Send Message</button>
    </div>
</form>

main.js

<script>
$(document).ready(function(){
    var form = $('#cform');
    
    form.submit(function(e){
        e.preventDefault();
        
        $.ajax({
            type: 'POST',
            url: '/send.php',
            data: form.serialize(),
            success: function(response){
                alert('Email sent');
                console.log(response);
            },
            error: function(a,b,c){
                alert('Could not send email');
                console.log(a,b,c)
            }
        });
    });
});
</script>

sendmail.php

<?php

$name = $_POST['name'];
$email = $_POST['email'];
$subject = $_POST['subject'];
$message = $_POST['message'];

if($name == '' || $email == ''){
    echo 'Name and email are required';
}
else{
    $headers  = "From: ShineExtreme <info@shineextreme.co.ke>\n";
    // $headers .= "Cc: Victor <wvictormbuguah@yahoo.com>\n";
    $headers .= "Cc: William <willyk99@gmail.com >\n";
    $headers .= "X-Sender: $name <$email>\n";
    $headers .= 'X-Mailer: PHP/' . phpversion();
    $headers .= "X-Priority: 1\n";
    $headers .= "Return-Path: info@shineextreme.co.ke\n";
    $headers .= "MIME-Version: 1.0\r\n";
    $headers .= "Content-Type: text/html; charset=iso-8859-1\n";
    
    mail($to, $subject, $message, $headers);

    echo 'Email sent...';
}

?>