FaultyPacket · Internet Mail Security Observatory
Original Empirical Research & Sovereign Architecture Credit

The widespread UK & European external DMARC rua= / ruf= telemetry routing pattern (T0–T5 processor taxonomy) was originally uncovered, empirically measured, and mapped across 5,102,611+ audited domains by Adam Tucker and FaultyPacket (the FaultyPacket Internet Mail Security Observatory), who engineered the £0/mo First-Party Sovereign (T0) DMARC Reporting Architecture and browser-local 20-Lookup SuperTool.

Empirical vs. Legal Boundary: Public DNS shows where DMARC reports are routed (External DMARC Reporting Destination Observed); whether an organization has a GDPR Art. 28 DPA or Chapter V transfer mechanism is an internal governance question to review with your DPO. Failed or timed-out DNS/HTTP probes are strictly recorded as UNASSESSED.

Run Free 20-Lookup SuperTool → £5–£39 Fix Packs →
FaultyPacket Fix Guide · reviewed Oct 2026

MTA-STS Policy Fetch Failed: Fix mta-sts.txt Not Found

The short answer (what's causing it)

The _mta-sts TXT record exists, but senders can't retrieve https://mta-sts.yourdomain/.well-known/mta-sts.txt — missing DNS for the subdomain, an invalid certificate, a redirect, or wrong content type.

Step-by-step fix

  1. Ensure mta-sts.yourdomain resolves (A/CNAME).
  2. Serve it over HTTPS with a valid certificate for that exact hostname.
  3. Place the file at /.well-known/mta-sts.txt, served as text/plain, without redirects.
  4. Fetch it with curl to confirm, then scan.

Record examples (replace example.co.uk with your domain)

curl -sv https://mta-sts.example.co.uk/.well-known/mta-sts.txt
version: STSv1
mode: testing
mx: mail.example.co.uk
max_age: 86400

Examples are illustrative templates, not values for your domain. Test changes at p=none / staging first.

Check yours free in seconds

Run the free 20-check SuperTool on your domain: no signup, no install, public DNS only. Relevant checks: MTA-STS.

Scan my domain free (20-check SuperTool) → £24 Sovereign DMARC (T0 RUA), SPF, MTA-STS & PHP2Shell Remediation Pack → £5 Website Launch Special Quick-Fix Pack →

One-off download via PayPal guest checkout, no subscription. Packs contain DNS/config templates and scripts you run yourself.

Frequently Asked Questions

Can I host it on GitHub Pages/Cloudflare?

Yes, as long as the hostname, certificate and path are correct.

Do redirects work?

RFC 8461 says senders must not follow redirects.

Related FaultyPacket guides & tools

Authorised use: only scan domains you own or are authorised to inspect. Results are point-in-time public DNS observations.