Sender Policy Framework — a DNS TXT record that lists which mail servers are allowed to send mail for your domain. Receiving servers check incoming mail against this list to spot spoofing.

What does "all" mean at the end?

"-all" rejects mail from anywhere not explicitly allowed. "~all" soft-fails (accepts but marks). "?all" is neutral (don't use). "+all" allows anything (never use — defeats the point of SPF).

Why does my SPF record warn about "too many DNS lookups"?

SPF spec limits you to 10 DNS lookups during evaluation. Each include: counts as one. Too many includes means receiving servers may abort the check.

SPF Checker

Look up and interpret any domain's SPF record. Flags common misconfigurations.

Check a domain's SPF

SPF record

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