TL;DR: Luxembourg data enrichment is the hardest phone job we run. Kaspr gave us 13 Luxembourg numbers in October 2026 and none were usable. All of them were foreign mobiles or office lines. In our first benchmark (15,000 enrichments run in 2025 and 2026, published May 2026), 40% of the mobiles found for one law firm list had US country codes. Keep your providers, add one that is strong on Benelux, and check every number before your team dials.
0 of 13.
That is how many usable Luxembourg mobiles Kaspr gave us in October 2026. Kaspr is our biggest phone source. Across Europe, 73% of the numbers it gave us were usable (2,111 of 2,879). In Luxembourg, every number was a foreign mobile or an office line.
Luxembourg breaks phone data, and the reason is simple. Many people who work there live in France, Belgium or Germany. Their phones come from home. Senior staff at global banks, funds and law firms keep a US mobile for years after they move.
Answrd is part of Profitbl, which runs cold calling campaigns across Europe. Here is what we found in Luxembourg in our first benchmark and in October 2026, and what we do about it.
Why is Luxembourg data enrichment so hard for phones?
Luxembourg data enrichment is hard for phones because the phone a person carries often belongs to another country. A large share of the people who work in Luxembourg cross a border each day. They keep the mobile plan from where they live. Senior staff at global firms move between offices and keep the number from an old posting.
Providers do not know any of this. They see a profile that says Luxembourg and a mobile that starts with +33, +32, +49 or +1. They return the number. Your fill rate looks fine.
Then your rep dials a French number for a Luxembourg compliance head. Or a US number for a partner who left New York years ago. Or the front desk of a fund administrator.
A Luxembourg mobile starts with +352 6. Office lines in Luxembourg start with other digits. That one check tells you a lot about what a provider gave you. It still cannot tell you whether the right person picks up.
What did our first benchmark and October 2026 data show?
Our data showed Luxembourg as the most mixed-up country we measured, in our first benchmark and again in October 2026. Each round found the same thing: Luxembourg contacts carry phones from other countries.
First benchmark (2025 to 2026): fill and format
The first benchmark covered 15,000 enrichments, run in 2025 and 2026, across 28 companies and 12 countries. More than 350 of them were Luxembourg contacts. Here is what still holds:
- 138 contacts at international law firms with Luxembourg offices: 40% of the mobiles found had US country codes. These were real US mobiles, on profiles that list Luxembourg as the place of work.
- 117 finance security contacts in Luxembourg and Belgium: ContactOut returned a real mobile for 56% of its finds. The rest were landlines, switchboards or numbers in the wrong format. That was its worst sample in the whole study.
- Wiza, Forager and Datagma: 95% to 100% of their Luxembourg finds were in mobile format. That counts the format of the number. It says nothing about who answers.
That data measured fill and format only. It also carried a caveat that still holds. The provider placed first in a waterfall sees every contact. Later providers only see the leftovers. So a win share tells you more about position than quality.
We ran those earlier lists through Clay. Profitbl cancelled Clay on 22 April 2026. Our waterfall now runs in-house, built in Claude Code.
October 2026: usable numbers and dial outcomes
We ran Tomba, FullEnrich and the other newer providers through looot, our data gateway. The October round added two things: a strict count of usable numbers, and dial outcomes. A usable number is a mobile, in the contact's own country, that we did not already know was bad. Reached the person means we dialled it on a live campaign and the right person answered.
Here is the Luxembourg picture, October 2026:
- Kaspr in Luxembourg: 0 usable of 13. All foreign mobiles or office lines. Belgium came next worst at 16 of 40 (40%). France came in at 540 of 725 (74%).
- 461 senior IT and security contacts in the Netherlands, Belgium and Luxembourg, 50 to 249 staff: Kaspr alone found a usable mobile for 225 (49%). Tomba, Eficia and the rest of the waterfall took it to 392 (85%). 20 of the misses had only a mobile from a neighbour country. These were Luxembourg staff on Belgian or French numbers.
- Eficia on that same list: 133 usable of the 205 contacts it tried (65%). 33 of its fails were wrong-country numbers.
So the first benchmark story holds. The waterfall rescued most of that list. Many of the contacts left over were Luxembourg staff still carrying phones from somewhere else. Every provider we ran finds those phones. The Dutch rows on that list were the easy part, as our Netherlands post shows.
Is a French mobile for a Luxembourg contact always wrong?
No. A cross-border mobile can still belong to the right person. A manager who lives in Metz and works in Luxembourg City may use a French mobile for everything. Our own-country rule drops that number. That is a choice, and it has a cost.
We make that choice for two reasons.
First, a mobile from a neighbour country is more often a private phone. A sales call to a private phone annoys people, and some of them will raise GDPR on the call. GDPR Article 5 also asks you to keep personal data accurate. A private phone filed as a work number is hard to defend.
Second, the cost was small on our list. 20 of 461 contacts had nothing but a neighbour-country mobile. That is about 4%. We would rather lose 4% than spend the first calls of a campaign on people who feel ambushed.
If Luxembourg is your whole market, 4% may be too much to give up. Then keep those numbers in a second pile. Check them, and dial them after the own-country ones. Many of them are French numbers. Our post on the best data providers for France shows how French mobiles behave at home.
A US mobile on a Luxembourg contact is a weaker bet. In our 2025 to 2026 data, they showed up on law firm staff who had worked in the US before. Put them at the very end of the queue.
Which providers work in Luxembourg?
Our Luxembourg sample is too small to rank providers on Luxembourg alone. Here is what we can say, with the n behind each line.
One caveat first. The October providers below ran after Kaspr, and often after Eficia too. They got the hardest contacts. Their rates show what is left after the big two.
- Kaspr: 0 usable of 13 in Luxembourg (October 2026). Strong elsewhere, with 73% usable across Europe. We have dialled Kaspr numbers on our campaigns.
- Eficia: we use Eficia. 65% usable on the 461-contact Benelux list after Kaspr (October 2026). Most of its fails there were wrong-country numbers. We have no Luxembourg-only count.
- FullEnrich: 38 usable of 52 on senior security contacts in the Netherlands, Belgium and Luxembourg, after Kaspr (October 2026). That was its best area for us. It did worse on mid-level staff at global companies: 15 of 97 after Eficia, with many US or foreign numbers.
- Tomba: 31 usable of 236 on Benelux contacts after Kaspr, for USD 1.78 (October 2026). About USD 0.05 per usable number, the cheapest we have. It bills on hits only.
- Lusha: we have dialled Lusha numbers. On a Benelux senior list: 27 billed hits from 58 calls and 1 usable own-country mobile, about USD 20 per usable number (October 2026). Most hits were foreign mobiles and direct lines.
- AI Ark: 0 usable of about 170 contacts (October 2026). Its hits were neighbour-country or foreign mobiles. That is the Luxembourg problem in one line.
- ContactOut: 56% real mobiles on 117 finance security contacts in Luxembourg and Belgium (2025 to 2026). We did not run it in October.
- Wiza, Forager and Datagma: 95% to 100% mobile format on their Luxembourg finds (2025 to 2026). We did not run them in October.
- A cheap tier of six low-cost providers: about 1% usable on about 250 senior European contacts (October 2026). Most hits were US numbers for US-based people. Luxembourg sets that exact trap.
Our view: the provider matters less in Luxembourg than the rule you put after it. Every source here returns foreign numbers for Luxembourg staff. Our Belgium post shows the same pattern one border over.
How many Luxembourg mobiles reach the right person?
We do not have enough dialled Luxembourg numbers to say. Kaspr gave us none usable to dial, and the rest of our Luxembourg finds sit inside Benelux lists.
Across Europe, about 1 in 4 dialled usable mobiles reached the right person in October 2026. That is the accuracy layer our May report promised. Here it is:
- Kaspr: 301 reached of 1,071 dialled (28%).
- Eficia: 60 reached of 233 dialled (26%).
- Kaspr in the Netherlands: 37 of 106 (35%).
- Kaspr in Belgium: 8 of 19, too few to call.
The rest rang out, went to voicemail or reached someone else. Until we have Luxembourg dial data, plan for the same 1 in 4 on a clean +352 mobile. Switching provider rarely fixes that, as we show in why Lusha and Kaspr mobiles reach the wrong person.
What should you do before you dial Luxembourg?
Keep the providers you have and add one that does well on Benelux senior contacts. Then sort and check the numbers before anyone dials. Here is what we do:
- Keep your stack and add one or two providers. After Kaspr, FullEnrich (38 usable of 52) and Tomba (31 of 236, for USD 1.78) did best for us on Benelux (October 2026). Tomba is cheap enough to add without a second thought.
- Sort by country code. +352 mobiles first. Neighbour-country mobiles (+33, +32, +49) in a second pile. US and other distant codes last.
- Log which provider found each number. You need it to see which step adds new Luxembourg numbers. You also need it when a prospect asks where you got their number.
- Check every number before the team dials. More providers means more numbers. More numbers means more wrong ones. In Luxembourg, a big share of the wrong ones are foreign mobiles and office lines.
Our waterfall enrichment guide covers how to order the steps and why the hit rate misleads. A line check alone will not catch the private and job-change numbers, as we explain in the limits of HLR lookups.
That last step is the job Answrd does. You upload the numbers your providers found. You get back the ones that pick up, with wrong and dead ones flagged. Your first 100 numbers are free.
For the full picture across 12 countries, read our European B2B data enrichment report.
Frequently Asked Questions
Why does Luxembourg break phone enrichment?
Many people who work in Luxembourg live in France, Belgium or Germany and keep a phone from home. Senior staff at global firms keep mobiles from old postings. Providers return those numbers. Kaspr gave us 0 usable Luxembourg mobiles of 13 in October 2026.
Should I drop a Luxembourg contact with a French or Belgian mobile?
We drop them from the first pile and keep them for later. A cross-border mobile can be the right person. A strict own-country rule drops them, and that is a choice. On our 461-contact Benelux list it cost 20 contacts, about 4%. If you keep them, dial them after the +352 mobiles.
What about US numbers on Luxembourg contacts?
In our first benchmark, 40% of mobiles found for 138 law firm contacts with Luxembourg offices had US codes. They showed up on staff who had worked in the US before. Put them at the end of your queue.
Which provider is best for Luxembourg mobiles?
Our Luxembourg sample is too small to name one. On senior security contacts in Benelux, FullEnrich found 38 usable of 52 after Kaspr, and Tomba was the cheapest per usable number (October 2026). The rule you run after the provider matters more.
How do I spot a Luxembourg mobile?
A Luxembourg mobile starts with +352 6. Office lines start with other digits. That check sorts the format. It cannot tell you if the right person will answer.
Check your Luxembourg numbers before you dial
Luxembourg data enrichment is where phone data goes wrong the most. Keep your providers, add one that is strong on Benelux, and sort every number by country. Then judge the list by how many mobiles reach the right person.
Run your next Luxembourg list through a check before the call block. Test 100 numbers free, no card needed. If you would rather talk it through, book a 15-minute call.