SpamCipher A2 measurement bundle - SPF/DMARC deployment over Tranco top-1M (2026).
Reproduce: pip install dnspython; python3 measure_auth.py  (A2_SEED env selects the seed).
Pinned Tranco list: 94VW2 (https://tranco-list.eu/list/94VW2), 2026-07-05.
Files: measure_auth.py (scanner), results_summary_seed{42,7}.json (aggregates + Wilson CIs),
sample.txt / sample_seed7.txt (exact sampled domains), raw_results.csv.gz (per-domain, seed 42).

--- OpenINTEL longitudinal (v3) ---
openintel_trend.py            extraction: DuckDB over OpenINTEL public Tranco parquet, 2022-2026.
openintel_tranco_trend.tsv    derived SPF/DMARC/policy/rua by snapshot.
Source: OpenINTEL (openintel.nl), CC BY-NC-SA 4.0, non-commercial research use.
