SPF Lookup Limit (10 DNS Lookups) – Why It Exists & How to Stay Under
SPF allows at most 10 DNS lookups when a receiver evaluates your record. Exceeding the limit causes a permerror and can hurt deliverability. Here’s what counts as a lookup and how to stay under.
What counts as a lookup
Each of these can consume one or more lookups: include: (each include is resolved and may trigger more lookups), a, mx, ptr, exists:, and redirect=. The total across the entire evaluation must not exceed 10.
Why the limit exists
Without a cap, a single SPF check could trigger many DNS queries and slow down mail acceptance. The 10-lookup limit keeps evaluation fast and predictable for receivers while still allowing typical multi-ESP setups when used carefully.
Common mistakes
- Chaining many
include:mechanisms (each can add several lookups). - Keeping includes for ESPs you no longer use.
- Not testing after adding a new include; the total can creep over 10.
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FAQ
What counts as an SPF lookup?
Each mechanism that requires DNS resolution: include:, a, mx, ptr, exists, and redirect. The receiver follows each and counts lookups until the limit (10) is reached.
Why 10 lookups?
To prevent excessive DNS load and slow evaluation. Early SPF had no limit; the 10-lookup cap was adopted to keep checks fast and predictable.
What happens if I exceed 10?
Receivers typically return a permerror. Your SPF may be treated as fail or invalid, which can affect deliverability and DMARC evaluation.
Can I reduce lookups without changing providers?
Yes. Remove unused includes, use SPF flattening if your ESP supports it, or move some sending to a subdomain with a shorter record.
Related reading
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