Mail server reverse DNS · UK small companies
What share of UK small companies have a mail server with no reverse-DNS (PTR) record?
5.3% of UK small companies (95% CI 3.72–7.51%), measured across 547 companies on 2026-10-01.
Measured every Friday since 2026-08-01 — 12 observations to date. Last measured 2026-10-01.
How this is measured
Tier 0. Resolve the MX, then PTR on the reversed address (bounded DNS query). Denominator: has_mx.
Passive measurement: a single DNS lookup, TLS handshake, or homepage GET per domain. Aggregate-only; no individual company is named. 95% Wilson confidence intervals. Population: national company registries (Companies House, Brreg, SIRENE), sampled by size band and resolved to email-active domains. Parked domains excluded. Snapshot: uk-companies-house-per600-seed20260728.
Licensed CC BY 4.0 — reuse with attribution to Quiet Failures. Download: JSON · CSV.
Why it matters
Missing reverse DNS is a classic quiet failure — nothing breaks visibly, but receiving mail systems downgrade or reject on it, so outbound deliverability degrades in ways that surface as "our email sometimes doesn't arrive".
The same check, other segments
- France small companies10.12%
- France micro companies9.05%
- France companies8.45%
- France large companies8.43%
- UK newly-formed (no accounts filed) companies8.33%
- France medium companies5.67%
- global domains5.46%
- UK companies4.8%