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spf 10 lookup limit

Authentication

SPF Flattening Explained: When to Flatten, When to Restructure (2026)

Alaa 27 August 2026

SPF has a hard 10 DNS lookup limit per evaluation (RFC 7208). Exceed it and you get PermError, breaking DMARC alignment. Flattening replaces includes with raw IPs to work around the limit, but ...