The MCP spec lands in 48 hours. I scanned 671,693 domains first. The layer under your email agents is rotting.

AgentMail. Cloudflare Email Service. Resend's agent SDK. Every AI SDR startup on Product Hunt this month. The pitch is always the same: "one API call and your agent has an inbox."

Cool. I went and measured the ground they're all standing on.

671,693 domains with MX records. 634,220 with SPF. 468,749 with DMARC. Daily forward-DNS scan of the Tranco top-1M, snapshot 2026-07-25.

Here's the number that should ruin your afternoon:

Last month the internet added 9,173 net new DMARC domains. DMARC enforcement went DOWN 0.42 percentage points.