Email Authentication Adoption Among the World's Most-Visited Websites: A 2026 DNS-Based Snapshot

A DNS-based measurement of SPF, DKIM, and DMARC adoption across the top 1,000 domains in the Tranco list. 76.0% publish SPF, 72.5% publish DMARC (but only 44.4% enforce it at p=reject), and 46.7% have a discoverable DKIM record under common selector names. 21.2% of the sample has none of the three mechanisms detectable. Dataset (CSV) and full methodology/limitations writeup (Markdown) included. Published by EmailSecurityGrade (emailsecuritygrade.com), a free tool for checking any domain's email authentication setup.