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Q & A Email Authentication · August 21, 2026

I added all my senders to SPF but emails still fail. Why?

The most common cause is exceeding the 10 DNS lookup limit. Each include:, a:, and mx: mechanism in your SPF record that requires a DNS lookup counts toward the limit. Many include: directives themselves expand into multiple lookups. Use DomainScan’s SPF checker to see your current lookup count. If it’s over 10, some lookups are skipped and the record breaks.

Read the full guide
How to Fix SPF Failures (softfail, hardfail, permerror)
SPF softfail, hardfail, permerror, and DNS lookup limit errors each have a different fix. This guide walks through diagnosing each failure type and rewriting your SPF record correctly — without breaking it.
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How do I know if SPF is causing my email to go to spam? My ESP (Mailchimp, SendGrid, etc.) says to add their SPF include. I did, but it still fails. What's the difference between SPF softfail (~all) and hardfail (-all)?