What is Letro¶
Letro is a secure messenger for work — it keeps your conversations, calls, and files end-to-end encrypted so that only you and the people you're talking to can read them.
Security note: Every message, call, and file in Letro is end-to-end encrypted by default. No one in between — not your network, not your IT team, not Letro itself — can read the content of your conversations.
Letro is built for people who handle sensitive information at work: finance, legal, healthcare, family offices, and other regulated or privacy-conscious teams. It looks and feels like the messaging apps you already use — a list of conversations, one-to-one chats and group silos, voice and video calls, files, and reactions — but the way it protects your data is different underneath.
What "end-to-end encrypted" means for you¶
When you send something in Letro, it's scrambled on your device before it leaves, and only the intended recipients' devices can unscramble it. It stays encrypted the whole way there and while it's stored.
In practice, this means the content of your messages can't be read by the servers that pass them along, by anyone who intercepts your connection, or by Letro as a company. You don't have to turn this on or think about it — it's simply how Letro works.
Because your keys live on your devices rather than on a server, Letro asks you to set up a secure backup and a recovery key early on. These let you get back into your encrypted history if you lose a device or sign in somewhere new. Setting them up takes a minute and is worth doing right away — see How Letro protects your messages.
Your Letro identity¶
In Letro, you're identified by a PostNumber. You use it to sign in and help other people find you without sharing a personal phone number or email address.
If you create your own account, you choose the numeric part of your PostNumber. It must be available and not reserved. A personal PostNumber looks like CH 6578 9.
If you're an organization member, your organization provides your PostNumber. It includes a country code, batch code, organization prefix, and member number, such as DE 0777 HSBC 0001. Your organization chooses the batch code and organization prefix.
Your PostNumber also helps people confirm that they're talking to the right person when they verify your identity.
The same experience across your devices¶
Letro runs on Web and Desktop, iOS, and Android, and your conversations stay in sync across all of them. You can start a chat on your laptop and pick it up on your phone. Each device you add is verified so you always know which of your own devices have access — and can remove any you no longer use.
Built for organizations¶
Many teams run Letro on a Letro Dedicated Server — a private, encrypted environment on dedicated infrastructure, with control over where data is stored (for example, keeping it in a specific country or region to meet data-residency rules). If your company handles regulated or confidential information, this is usually how Letro is deployed. Learn more in What is a Letro Dedicated Server.
Good to know¶
- You don't need to be technical to use Letro safely. The security features are designed to guide you, and this help center walks through each one step by step.
- End-to-end encryption protects the content of your conversations. Some operational information (such as which devices are active) is still needed to run the service — this is covered in the security section.
- If your organization provided your account, your sign-in method and server are usually already set up for you. You just download the app and sign in.
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