add_action('rest_api_init',function(){
  register_rest_route('indigo/v1','/lead',[
    'methods'=>'POST','permission_callback'=>'__return_true',
    'callback'=>function($r){
      $p=$r->get_json_params();
      if(empty($p['email'])||empty($p['first_name'])||empty($p['consent']))
        return new WP_Error('bad',__('Missing fields'),['status'=>400]);
      $ref='IM-'.str_pad((string)wp_rand(1,999999),6,'0',STR_PAD_LEFT);
      $to=get_option('admin_email');
      $subj='[Indigo Maenam] New enquiry '.$ref.' — '.sanitize_text_field($p['first_name'].' '.$p['last_name']);
      $body="Ref: $ref\nName: {$p['first_name']} {$p['last_name']}\nEmail: {$p['email']}\nPhone: {$p['phone']}\nCountry: {$p['country']}\nLooking for: {$p['profile']}\nTimeline: {$p['timeline']}\nBudget: {$p['budget']}\nPlot: {$p['villa']}\nContact via: {$p['contact']}\nMessage: {$p['message']}\nPage: {$p['page']}\nPDPA consent: yes";
      $ok=wp_mail($to,$subj,$body);
      if(!$ok) return new WP_Error('mail',__('Mail failed'),['status'=>500]);
      return ['ref'=>$ref,'ok'=>true];
    }
  ]);
});
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="https://indigomaenam.com/wp-sitemap-index.xsl" ?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"><sitemap><loc>https://indigomaenam.com/wp-sitemap-posts-post-1.xml</loc></sitemap><sitemap><loc>https://indigomaenam.com/wp-sitemap-posts-page-1.xml</loc></sitemap><sitemap><loc>https://indigomaenam.com/wp-sitemap-taxonomies-category-1.xml</loc></sitemap><sitemap><loc>https://indigomaenam.com/wp-sitemap-users-1.xml</loc></sitemap></sitemapindex>