Definition
SPF ten-lookup limit
The SPF ten-lookup limit is the RFC 7208 rule forbidding the evaluation of an SPF record from triggering more than ten DNS queries; beyond that, evaluation stops with a permerror and the record stops protecting the domain.
Every include, a, mx, ptr, exists and redirect counts as one lookup, and an include also counts everything it includes in turn. The ip4 and ip6 mechanisms are free: they trigger no query at all.
The threshold arrives sooner than people expect. A mailbox provider, an invoicing tool, a newsletter, a CRM and a booking system are often enough to go past ten, because a single vendor include can consume three or four on its own.
dig +short TXT example.com | grep spf1- Also known as
- 10 DNS lookup limit, too many DNS lookups, SPF permerror, void lookups
- Standard
- RFC 7208, §4.6.4