ip6 — SPF Mechanism

The SPF ip6 mechanism explicitly authorises an IPv6 address or prefix to send email. No DNS lookup required.

Type
Mechanism
Syntax
ip6:<ip6-address>[/prefix-length]
DNS Lookup
No — no extra lookup
Example
ip6:2001:db8::/32

💬 What This Mechanism Does

The ip6 mechanism works identically to ip4 but for IPv6 addresses. As more servers send from IPv6, omitting ip6: entries means those senders will fail SPF silently.

When to Use This

  • Authorising an IPv6-addressed outbound mail server
  • Including an IPv6 prefix for a cloud provider's sending range

⚠️ Watch Out For

  • Does not count toward the 10-lookup limit.
  • Use CIDR notation carefully — IPv6 prefixes can accidentally cover enormous ranges.

📚 RFC References

↗RFC 7208 §5.6 — The "ip4" and "ip6" Mechanisms

🔗 Related SPF Elements

ip4
Mechanism
 include
Mechanism

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