MTA-STS Policy Generator

Build a valid MTA-STS policy.txt and the matching _mta-sts TXT record. Pick mode (testing or enforce), MX hosts and max_age — free, client-side only.



How to use it
  1. Start in testing so mail still flows if something is wrong; move to enforce only after reports look clean.
  2. List every MX that should receive mail for the domain. Wildcards such as *.mail.protection.outlook.com are allowed and cover Microsoft 365.
  3. Host the policy file at https://mta-sts.<domain>/.well-known/mta-sts.txt over HTTPS with a valid certificate for that host.
  4. Publish a TXT record on _mta-sts.<domain> with v=STSv1; id=<version>. Change id whenever you update the policy so receivers refetch it.


Audit hundreds of domains at once
Need SPF, DMARC and MX checks across a whole client list? Run the Bulk SPF / DMARC / MX Auditor on Apify ($2 per 1,000 domains).
Want the full kit?
Runbooks, checklists and helpdesk templates: IT Admin Packs on Gumroad.