GUIDE
SPF explained: the 10-lookup limit and how to stay under it
SPF lists which servers may send mail for your domain. Too many includes and it silently breaks.
SPF (Sender Policy Framework) is a TXT record at the domain apex starting with v=spf1. It lists IP ranges and other domains (include:) whose servers may send on your behalf.
The 10-lookup rule
Receivers stop evaluating after 10 DNS lookups (include, a, mx, ptr, exists, redirect each count, recursively). Exceeding it returns PermError — effectively “no SPF”. Popular SaaS vendors often consume 2–4 lookups each, so five vendors can already break you.
How to fix it
- Remove vendors you no longer use.
- Replace
include:with the vendor’s literalip4:ranges where they are stable (“flattening”). - Move marketing platforms to a subdomain with its own SPF.
The SPF Lookup shows the full include tree and lookup count.