Send mail using ajax WP

sendmail.php

<?php 
add_action( 'wp_ajax_send_email', 'callback_send_email' );
add_action( 'wp_ajax_nopriv_send_email', 'callback_send_email' );

function callback_send_email() {
	$forms            = '[email protected]';
	$name             = $_REQUEST['name'];
	$email_add        = $_REQUEST['email_add'];
	$business         = $_REQUEST['business'];
	$business_address = $_REQUEST['business_address'];
	$url              = $_REQUEST['url'];
	$facebook_url     = $_REQUEST['facebook_url'];
	$source           = $_REQUEST['business'];
	$subject          = "[XYZ] Host Interest Form";
	$email_body       = "XYZ FORM<br><br>" .
	                    "Your name: $name. <br>" .
	                    "Your email: $email_add. <br>" .
	                    "Name of your business/operation: $business. <br>" .
	                    "Your address: $business_address. <br>" .
	                    "Your website address: $url. <br>" .
	                    "Your Facebook address: $facebook_url. <br>" .
	                    "How did you hear about Harvest Hosts?: $source. <br>";
	$to               = "[email protected]";
	$headers          = "MIME-Version: 1.0" . "\r\n";
	$headers          .= "Content-type:text/html;charset=UTF-8" . "\r\n";
	$headers          .= "From: $business <$forms> \r\n";
	$headers          .= "Reply-To: $email_add \r\n";
	$mail             = mail( $to, $subject, $email_body, $headers );
}

?>
    <script>
     jQuery(document).ready(function ($) {
            //Validate the form filed in next button click.
            $('#btn-validate').click(function (e) {
                var first_name = $('#input_name').val();
                var email = $('#input_email').val();
                var business_add = $('#business').val();

                $(".error").remove();

                if (first_name.length < 1) {
                    $('#input_name').after('<span class="error">This field is required</span>');
                }
                if (business_add.length < 1) {
                    $('#business').after('<span class="error">This field is required</span>');
                }

                if (email.length < 1) {
                    $('#input_email').after('<span class="error">This field is required</span>');
                } else {
                    var regExp = /^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
                    var validEmail = regExp.test(email);
                    if (!validEmail) {
                        $('#input_email').after('<span class="error">Enter a valid email</span>');
                    }
                }
                var errorClass = $(".first-form").find('.error');
                if (errorClass.length < 1) {
                    $(".first-form").hide();
                    $(".second-form").addClass('visible');
                    $('#become-host .host-heading').text('A Few More Questions');
                    $('#host-form__sub-heading p').text('About Your Business');
                    var name = jQuery('#input_name').val();
                    var email_add = jQuery('#input_email').val();
                    var business = jQuery('#business').val();
                    var business_address = jQuery('#business-address').val();
                    var url = jQuery('#url').val();
                    var facebook_url = jQuery('#facebook-url').val();
                    var source = jQuery('#source').val();
                    jQuery.ajax({
                        url: '<?php echo admin_url( 'admin-ajax.php' ); ?>',
                        type: "POST",
                        cache: false,
                        data: {
                            action: 'send_email',
                            name: name,
                            email_add: email_add,
                            business: business,
                            business_address: business_address,
                            url: url,
                            facebook_url: facebook_url,
                            source: source
                        },
                        success: function (res) {
                            console.log("Email Sent.");
                        }
                    });
                }
            });


        });
    </script>