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Email deliverability guide

Why your SPF record is failing

SPF failures usually come from stale DNS, missing vendors, too many lookups, or a mail migration that changed who sends for your domain.

Common SPF failure causes

  • More than one SPF TXT record exists for the same domain.
  • The service sending mail is not included in the SPF record.
  • The record exceeds SPF's DNS lookup limit because of too many includes.
  • The domain uses old include values from a previous mail provider.
  • Mail is being forwarded, rewritten, or relayed in a way SPF does not expect.

What to check first

Start with the exact domain in the From address, not just the root domain. Review current TXT records, identify every legitimate sender, remove obsolete providers, and test both direct mail and application-generated mail.

When to get help

If SPF, DKIM, and DMARC results do not agree, or messages fail only for certain recipients, Cyber Duct Tape can trace DNS, mail headers, and provider configuration for Lakewood, Denver metro, Colorado, and remote clients.