.uk is the country domain used in United Kingdom. Across 21,194 .uk addresses verified by BounceZero between April and October 2026, 17.0% were invalid, 3.7% catch-all, 10.6% unknown and 65.0% confirmed valid. Catch-all and unknown together mean a large share cannot be confirmed.
Every .uk address BounceZero verified for customers between April and October 2026, beside the corpus benchmarks. The remainder of each row to 100% is risky and role results.
| Segment | Addresses | Invalid | Catch-all | Unknown | Confirmed valid |
|---|---|---|---|---|---|
| .uk | 21,194 | 17.0% | 3.7% | 10.6% | 65.0% |
| All non-freemail domains (business and ISP) | 6,514,884 | 14.5% | 2.3% | 27.0% | 32.6% |
| Business domains only (consumer ISP and freemail excluded) | 1,269,919 | 22.9% | 9.4% | 22.5% | 40.3% |
| All freemail | 1,415,154 | 17.6% | 1.1% | 2.1% | 74.0% |
Non-freemail includes consumer ISP mailboxes; a business-only cut is on the benchmarks page. Method and every other cut: Lead List Quality Benchmarks 2026. Risky and role on the .uk row: 3.8%.
UK business domains verify well: moderate invalid share, low catch-all and few unknowns. Most unknowns are corporate gateways on large employers.
UK lists are business-heavy and verify well: few catch-alls, few unknowns, and most unknowns are corporate gateways at large employers. The invalid share is close to the business average and comes from staff turnover rather than from dead providers. PECR requires consent for individuals and sole traders and permits legitimate-interest email to limited companies with an opt-out, which makes the company-type of the contact the first filter and verification the second.
On confirmed-invalid rate, .uk ranks 10 of 23 country domains in the corpus, just behind .co at 17.1%, ahead of .com at 16.4%.
On unknown rate, .uk ranks 18 of 23 country domains in the corpus, just behind .br at 12.0%, ahead of .fr at 9.3%.
On confirmed-valid share, .uk ranks 2 of 23 country domains in the corpus, just behind .se at 92.0%, ahead of .it at 64.2%.
How to read these rates: they are BounceZero's probe outcomes on customer lists over April to October 2026, not a census of .uk mailboxes. Unknown and catch-all measure what verification could not confirm, which depends on the provider's gateway policy during the window as much as on the addresses. The lists are the ones customers chose to upload, so segments dominated by a few large uploads carry their age and source. Method and limitations: benchmarks page.
About one in 9 .uk addresses cannot be confirmed either way. That is gateway behaviour, not a verdict; route those contacts to phone or LinkedIn and re-check after a week.
17.0% of .uk addresses are confirmed invalid, close to the 14.5% seen across non-freemail lists. Delete them; there is nothing to re-check.
3.7% of .uk addresses sit behind a catch-all accept. Those cannot be confirmed; send to them only from a secondary domain at low volume.
With 65.0% of addresses confirmed live, .uk is a segment you can send to from the main domain without a second thought beyond re-verifying before every send.
A clean UK list should confirm two thirds valid. PECR applies to individuals and sole traders; limited companies can be approached on legitimate interest with an opt-out.
Role addresses such as info@ and sales@ make up 11.2% of .uk addresses in the corpus. Role addresses rarely reach a person; prefer named contacts.
17.0% of 21,194 .uk addresses verified by BounceZero between April and October 2026 were confirmed invalid, against 14.5% across non-freemail domains and 17.6% across freemail.
10.6%. Unknown means the mailbox could not be confirmed either way, usually because the gateway deferred the probe. BounceZero refunds unknown results; re-check after a week or use a second channel.
Partly: 3.7% of .uk addresses sat behind a catch-all accept, so the server took any address and the mailbox could not be confirmed.
65.0% confirmed valid at verification time. Keep bounces under 2% and complaints under 0.3% on the send, and re-verify the segment before every send.
Upload the file and see valid, invalid, catch-all and unknown per row, with the .uk segment against this benchmark. 100 free checks a month, unknowns refunded.
Ayoub built BounceZero's 5-stage validation pipeline, its dedicated BGP-announced IP infrastructure, and the Patroni HA PostgreSQL cluster behind every verification. Previously built high-volume email delivery infrastructure. Trained at 1337 Benguerir (École 42 network, 2019). Open-source: bgp_analyzer.
Invalid, catch-all and unknown rates per email provider and country domain, 2026
159,794 Telefónica addresses verified April to October 2026
246,811 TPG addresses verified April to October 2026
10,998 .us addresses verified April to October 2026
56,582 Windstream addresses verified April to October 2026
36,082 Xtra (Spark) addresses verified April to October 2026
21,081 Yahoo Mail addresses verified April to October 2026
Continue through related topics