Practical troubleshooting guide · The business scenario is illustrative, not a client case study. Administrative changes require authorised access.

A Niagara Falls tour operator might find that staff replies arrive while booking confirmations fail after an email-policy change. A retailer can encounter the same issue with order notifications. This guide addresses an authentication mismatch; it does not assume that every missing confirmation has the same cause.

Compare the visible and authenticated identities

Ask for the original headers of a test message and the platform’s failure log. Record the visible From address, Return-Path and DKIM signing domain. These identify different parts of the sending process. Work with a test booking that contains no customer information. Screenshots of a sent folder do not expose enough detail to diagnose the mismatch.

Understand the alignment requirement

DMARC checks whether a passing SPF or DKIM identity aligns with the visible From domain, under the domain’s alignment settings. A vendor can authenticate its own domain yet fail DMARC for your business address. Read Authentication-Results from the receiving system and distinguish spf=pass, dkim=pass and dmarc=pass instead of treating them as interchangeable results.

Fix the sender configuration

Use the platform’s supported custom-domain authentication setup and publish exactly the DNS records it supplies. Confirm the provider reports verification complete and sends with the intended identity. Do not switch an enforcing DMARC policy off merely to hide a broken integration. If staged policy changes are necessary, the administrator should review legitimate senders, reporting and the security tradeoff first.

Test each notification separately

Confirmations, cancellations and marketing campaigns may use different infrastructure. Test each relevant route and a customer reply, recording which template and sender were involved. If a platform cannot support an authenticated business identity, ask about its supported vendor-domain sender option. Keep the customer-facing reply destination clear, and request support using redacted headers rather than exporting your booking database.

MAKE IT ACTIONABLE

Your next steps

  • Compare From, Return-Path and DKIM domains.
  • Verify the platform’s custom-domain setup.
  • Check each transactional message type.

Official reference

Google: Set up DMARC

Technical guidance checked October 1, 2026. Product features and requirements can change. The business checklists above are practical suggestions from Cyber Bounds.

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