{
 "metric": "smtp-starttls",
 "segment": "gb-medium-large",
 "anchor": "company",
 "label": "UK medium & large companies",
 "population": "UK medium & large companies",
 "states": [
  "offered",
  "absent"
 ],
 "quiet_failure_states": [
  "absent"
 ],
 "measurement": "Connect to the lowest-preference MX on port 25, `EHLO`, check for the `STARTTLS` capability. Denominator: `has_mx`, further restricted to MXs that answer.",
 "why_it_matters": "If STARTTLS is not offered, every inbound message crosses the internet in plaintext, readable by anything on the path. The domain may have perfect SPF/DMARC and still be handing its mail over in the clear.",
 "limits": "~32% of small-company MXs never answer within a 6s timeout and are excluded, so this is measured over *reachable* mail servers.",
 "data_tier": "smtp",
 "population_predicate": "has_mx",
 "entity_type": "domain",
 "kind": "failure",
 "latest": {
  "day": "2026-08-14",
  "n": 425,
  "qf_pct": 1.18,
  "ci": [
   0.5,
   2.72
  ],
  "dist": {
   "offered": 98.82,
   "absent": 1.18
  },
  "snapshot": "uk-companies-house-per600-seed20260728"
 },
 "series": [
  {
   "day": "2026-08-02",
   "n": 412,
   "qf_pct": 0.73,
   "ci": [
    0.25,
    2.12
   ],
   "dist": {
    "offered": 99.27,
    "absent": 0.73
   },
   "snapshot": "uk-companies-house-per300-seed20260728"
  },
  {
   "day": "2026-08-04",
   "n": 427,
   "qf_pct": 0.94,
   "ci": [
    0.36,
    2.38
   ],
   "dist": {
    "offered": 99.06,
    "absent": 0.94
   },
   "snapshot": "uk-companies-house-per600-seed20260728"
  },
  {
   "day": "2026-08-05",
   "n": 428,
   "qf_pct": 0.93,
   "ci": [
    0.36,
    2.38
   ],
   "dist": {
    "offered": 99.07,
    "absent": 0.93
   },
   "snapshot": "uk-companies-house-per600-seed20260728"
  },
  {
   "day": "2026-08-07",
   "n": 422,
   "qf_pct": 0.95,
   "ci": [
    0.37,
    2.41
   ],
   "dist": {
    "offered": 99.05,
    "absent": 0.95
   },
   "snapshot": "uk-companies-house-per600-seed20260728"
  },
  {
   "day": "2026-08-14",
   "n": 425,
   "qf_pct": 1.18,
   "ci": [
    0.5,
    2.72
   ],
   "dist": {
    "offered": 98.82,
    "absent": 1.18
   },
   "snapshot": "uk-companies-house-per600-seed20260728"
  }
 ],
 "license": "CC BY 4.0",
 "source": "https://quietfailures.com/datasets/smtp-starttls/gb-medium-large"
}