One secure line to your clients.Verified identities.Private AI agents.

For law firms, wealth managers and trustees. Every exchange recorded, kept for ten years, and ready when the regulator asks.

Hosted in SwitzerlandAudited encryption libraryMobile apps pen-tested, Oct 2026
A glass-fronted studio on an alpine ridge at first light, a person working inside
Line · Identity · Private AI
01 · One line

One encrypted channel. What was sent, to whom, and when, on record

Letro letter: Q3 2026 portfolio report for the Vidal Family Trust, with a Seen by sheet listing each recipient and the date they read it
02 · Verified identity

One passport-verified person. Permanent · non-transferable

Letro identity screen: Claudia Brunner, PostNumber CH 4127, with message, call, video and verify options
03 · Private AI agents

Drafted by Letro Private AI · approved by a person

Letro workflow screen: Renew Q4 client mandates, owner, goal, inputs and connections
The problem

Sent isn't proof.

The client texted the payment change, the mandate went by email, and when someone asks what was agreed, the proof is a person's memory.

$2bn+

in fines for off-channel messaging

US regulators have fined more than 100 firms over WhatsApp and personal email since 2021. The messages were fine. The record didn't exist.

$3bn

lost to email impersonation in a year

Email verifies a domain, not a person. One changed character in a domain is enough, and the message now writes itself.

10 years

later, prove it

A regulator asks what was sent, to whom, and when. Screenshots are easy to dispute. A mailbox export shows only what one side kept.

Sources: SEC, remarks on off-channel recordkeeping, Nov 2024 · FBI IC3, 2025 Internet Crime Report, business email compromise losses

One line

Everything between you and a client, in one place.

Instructions, documents, approvals and formal letters move through one encrypted channel instead of email attachments, WhatsApp threads and registered post. Each exchange is timestamped and kept on record as it happens.

Clients join free, on iPhone, iPad, Android or the web.
Formal letters with proof of delivery and receipt. Registered post, without the post.
Roles and approvals built in, so the right person signs off before anything leaves the firm.
See what you can do with Letro →
Verified identities

You always know who is on the other end.

Every Letro account belongs to one real person, verified against a passport. The identity is permanent and can't be handed to anyone else, so an instruction from a client is from that client, not from whoever controls an inbox. We call it a PostNumber.

Someone not on Letro yet? Reach them by email: they get a free temporary room, and an invitation to get their own PostNumber.

How PostNumber works →
Portrait of a client in warm window light
Verified
CH 5670
NameRegula Baumann
CountrySwitzerland
Permanent · non-transferable
Private AI agentsIn preview

AI that works for your firm, and only inside it.

Letro Private AI reads the mandate, drafts the reply and prepares the approval, inside an isolated environment that Letro operates in Europe for your organisation alone. Nothing goes to a public model provider. Nothing trains anyone's model.

Review a 60-page mandate and surface what changed.
Draft the reply in your house style, ready for a person to approve.
Prepare the next step of a client instruction, for a person to sign off.
See how Private AI works →
Letro Agents screen on iPhone: Company Brain available. Only you can see your conversations. Asking never runs workflows, sends messages or changes records.
Why firms can rely on it

Open protocol. Independently tested. Swiss hosting.

Built on Matrix, the open communication standard chosen by several European governments; its encryption library (vodozemac) audited by Least Authority; mobile apps penetration-tested by ImmuniWeb in October 2026; hosted in Switzerland. ISO 27001 planned for 2027.

Wavestone
Swiss Cybersecurity Startup Radar 2026
Swiss Startup Association
Founder interview →
Least Authority
Encryption library audited (vodozemac, 2022)
ImmuniWeb
Mobile app penetration test, October 2026
Visit the Trust Center →

See Letro on your own cases in 30 minutes.

Bring a real client scenario. We'll show you the line, the verified identity on each end, and the record it leaves.

From CHF 12 per seat. Founding firms: first 3 months free →