SPF include chain health check

Track vendor bundles, deep includes, and planned changes. Keep headroom (≤8 lookups), cap depth at ≤3, and avoid cycles. Flatten only long‑term stable ranges.

Steps

1. Fetch TXT and expand includes; graph the chain
2. Count include/a/mx/ptr/exists/redirect toward the 10 cap
3. Classify sources (stable vs volatile) and consider flattening the stable ones
4. Stage on a sub‑domain; monitor 24–48h; then cut over

Pitfalls

• Hidden recursion and loops; cap depth ≤3
• Macros and ptr/exists inflating lookups
• Duplicate TXT records; receivers may choose arbitrarily