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SPF Mechanisms Guide — Use our tool to verify each mechanism is working as intended. Test Mechanisms →

What are SPF mechanisms (e.g., ip4, a, mx, include)?

Mechanisms define which servers are authorized. The main ones are:

  • ip4 authorizes a specific IPv4 address or range.
  • a authorizes the IPs of the domain’s A record.
  • mx authorizes the IPs of the domain’s MX records.
  • include imports the SPF policy of another domain.

Mechanisms are the items on the ship registry showing which vessels carry the domain’s colors.

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