What is SPF?
SPF (Sender Policy Framework) is an email authentication method that specifies which mail servers are allowed to send email for a domain.
What do the qualifiers mean?
"-all" means fail (hard), "~all" means softfail, "?all" means neutral, "+all" means pass all (not recommended).
What errors can be detected?
We detect syntax errors, too many DNS lookups (>10), missing records, multiple SPF records, and deprecated mechanisms.
How many DNS lookups are allowed?
SPF allows a maximum of 10 DNS lookups (includes, a, mx mechanisms). Exceeding this causes validation failures.
Should I use -all or ~all?
"-all" is stricter and tells receivers to reject unauthorized mail. "~all" is softer and marks as suspicious. "-all" is recommended once you're confident in your configuration.
How does this relate to DKIM and DMARC?
SPF verifies the sending server. DKIM verifies the message wasn't altered. DMARC ties them together with policy enforcement.
