CloudFlare Worker for MTA-STS policy

mta-sts.js

const mode= 'testing';
//const mode= 'enforce';
const max_age= 604800; // 1 week
const mx_list = [
   'aspmx.l.google.com'
  ,'aspmx2.googlemail.com'
  ,'aspmx3.googlemail.com'
  ,'aspmx4.googlemail.com'
  ,'aspmx5.googlemail.com'
  ,'alt1.aspmx.l.google.com'
  ,'alt2.aspmx.l.google.com'
];

const sts= `version: STSv1
mode: ${mode}
${mx_list.map(i=> 'mx: '+i).join('\n')}
max_age: ${max_age}`;

addEventListener('fetch', evt=> {
  return evt.respondWith(new Response(sts));
});