SPF flattening guide
SPF flattening replaces include-based SPF logic with explicit IPs gathered from those includes. It can solve lookup-limit problems, but it also creates maintenance risk.
Why flattening exists
Flattening is often used when a domain relies on too many third-party includes and starts approaching or exceeding the SPF lookup limit.
Benefits of flattening
- Can reduce lookup count dramatically.
- Can improve reliability where multiple providers are involved.
Risks of flattening
- Third-party provider IPs can change.
- Static flattened records become stale.
- Automation can hide complexity instead of reducing it.
Better option: simplify the number of sending services where possible before relying on flattening.
Best practice
If you flatten, automate it carefully, monitor changes and document exactly which providers are included. Keep the record reviewable by humans.