Wordpress Create custom fields and send mail

functions.php

add_action('post_submitbox_misc_actions', 'send_to_user_block');
function send_to_user_block()
{
	global $pagenow;
	
    $post_id = get_the_ID();

    if (get_post_type($post_id) != 'post') {
        return;
    }
	
	if (in_array( $pagenow, array( 'post.php'  ) )){
		$userNameValue = get_post_meta($post_id, 'user_name_field', true);
		$userEmailValue = get_post_meta($post_id, 'user_email_field', true);
		wp_nonce_field('my_custom_nonce_'.$post_id, 'my_custom_nonce');
		
		echo '<div id="send-to-user-block" class="misc-pub-section" style="border-top-style:solid; border-top-width:1px; border-top-color:#EEEEEE; border-bottom-width:0px;">
		<input type="text" name="user_name_field" placeholder="Name" id="user_name_field" value="">
		<input type="text" name="user_email_field" placeholder="Email" id="user_email_field" value="">
		<input id="send_mail" class="button button-highlighted" type="submit" value="Send Mail" name="send_mail">
			</div>';
	}
}

add_action('save_post', 'sendMail');
function sendMail( $post_id )
{
	if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) {
        return;
    }
	if (!isset($_POST['my_custom_nonce']) || !wp_verify_nonce($_POST['my_custom_nonce'], 'my_custom_nonce_'.$post_id)) {
        return;
    }
	if (!current_user_can('edit_post', $post_id)) {
        return;
    }
    if (isset($_POST['user_name_field']) && isset($_POST['user_email_field']) && isset($_POST['send_mail']) && $_POST['send_mail'] == 'Send Mail') {
		if(get_permalink($post_id) && sanitize_email($_POST['user_email_field'])) {
			$name = sanitize_text_field($_POST['user_name_field']); 
			$email = sanitize_email($_POST['user_email_field']);
			$msg = 'Hi '.$name.',<br> <a href="'.get_permalink($post_id).'">View Your Story</a>'; 
			mail($email,"Your Story",$msg);
		}
	}
}