email-auth · severity medium
MTA-STS
Share of email-active domains with no enforcing MTA-STS policy (absent, or testing mode only).
Measured every Monday · last updated
How it is measured
Tier 0 + 3a. TXT at _mta-sts.<domain>; if present, fetch https://mta- sts.<domain>/.well-known/mta-sts.txt and read mode. Denominator: has_mx.
Why it matters
The declared-vs-enforcing split is exactly the brand thesis. mode: testing publishes a policy, produces reports, and does not require TLS — downgrade attacks still work. The DNS record alone looks like adoption; only the fetched policy reveals whether it bites.
The base rate
Two independent populations. The global, domain-anchored figure is unbiased; the company-anchored figures are built by matching company names to domains and skew toward more digitally-mature firms. Both are published, so the gap is visible.
By company size band
Company-anchored cuts (national registries with a size proxy), split by size band. Right-hand figure is the share not meeting the control.
Every segment
Pick one to see the citable answer for a company like yours, with its trend and methodology.
Show the remaining 62 segments
Slices below 100 measured members are withheld rather than shown with a wide interval — an absent country or issuer means too little data, not zero failures. Licensed CC BY 4.0. Machine-readable data per segment: append .json or .csv to its URL.