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 5,242,611+ 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.

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FaultyPacket Fix Guide · reviewed Oct 2026

compauth=fail reason=000: What It Means in Microsoft 365 and How to Fix It

The short answer (what's causing it)

Microsoft's composite authentication header shows reason=000 when the message failed explicit DMARC for the sender's domain — neither aligned SPF nor aligned DKIM passed.

Step-by-step fix

  1. Read the full Authentication-Results header for spf, dkim and dmarc values.
  2. If it's your domain: fix the sending source's SPF/DKIM alignment.
  3. If it's a partner: tell them their mail fails DMARC (observation, not accusation).
  4. Avoid broad allow-list overrides that bypass spoof protection.

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

Authentication-Results: spf=fail smtp.mailfrom=example.co.uk; dkim=none; dmarc=fail action=quarantine header.from=example.co.uk; compauth=fail reason=000

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: SPF, DKIM, DMARC.

Scan my domain free (20-check SuperTool) → £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

What about reason=001 or 601?

Other codes indicate implicit authentication outcomes; check Microsoft's documentation for each.

Can I whitelist it?

Possible, but it masks a real authentication gap.

Related FaultyPacket guides & tools

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