HexomailYour data and security
Updated on 14 October 2026
The short answer: your email does not go through our servers.
Hexomail is an email client: an app installed on your computer or phone that connects directly to your provider's servers (Gmail, Orange, your hosting provider…) to fetch and send your messages. It is not an email service: your addresses stay with your current provider, which keeps storing your messages and can still read them, just as it does today. Hexomail protects you from senders who track you, not from your provider.
Our servers are only involved in optional or technical services, all detailed below, including the rare cases where data about you passes through them. The privacy policy gives the legal version.
In short
- Your messages
- Never on our servers.
- Your passwords
- Never, except encrypted for your new device when you add it: unreadable to us.
- Search
- Entirely on your device.
- Advertising and analytics
- No advertising. No analytics in the app; on this website, an anonymous count of visits, without cookies, hosted by us (details).
- The web version
- End-to-end encrypted between your device and the browser: our server relays without being able to read.
- Mailing lists
- The exception: the addresses of subscribers to a list hosted by us are on our servers, encrypted.
- Optional services
- Automatic settings, image proxy, opaque links, HexoTransfert, sync and the web version go through our servers, without us being able to read your messages.
Which data goes where
| Data | Your device | Hexonest servers |
|---|---|---|
| Content of your messages and attachments | Yes, encrypted local database | Never |
| Email passwords | Yes, system keyring | Never, except when adding a device: encrypted for that device only, unreadable to us |
| Google sign-in token (Gmail) | Yes | Never: sign-in happens between your device and Google |
| Search index | Yes | Never |
| Domain of your address, when adding an account | — | Yes, to find the settings; never the full address |
| Synced accounts, signatures and settings | Yes | Encrypted on your devices, unreadable to us |
| HexoTransfert files | Yes | Never: they travel inside your emails |
| HexoTransfert public keys | Yes | Yes, published so that people can write to you |
| Addresses of mailing list subscribers | Only for the duration of a send | Yes, encrypted, with proof of their consent |
| Messages displayed in the web version | Yes, the device is what sends them to the browser | Relayed end-to-end encrypted, unreadable to us, never stored |
| IP address | — | Seen when the app contacts our services, as with any website |
Gmail and other providers
With most providers, Hexomail signs in with your password (or an app password), stored in your system's keyring.
Google. You sign in on Google's official page (which currently shows an “unverified app” warning, see why). The permission requested is full access to Gmail, the only way to fetch and send your messages over IMAP and SMTP. The exchange with Google happens on your device: your Google password, your access tokens and your messages never go through our servers.
Microsoft. Microsoft accounts (Outlook, Hotmail, Live, Microsoft 365) are not supported for now: Microsoft no longer accepts passwords for these mailboxes, and Hexomail does not offer Microsoft sign-in.
Automatic settings. When you add an address, Hexomail asks our server for the IMAP and SMTP settings of its domain (the part after “@”). The server looks them up in public settings databases and in the domain's DNS. Your full address is never sent.
Trackers, images and links
Images. Remote images are not loaded until you ask: they are how the sender knows that you opened their message, and from where. Spy pixels are detected and never loaded. SVG images are converted to plain images on your device, which neutralises any code they may contain.
Cleaned links. Before opening a link, Hexomail removes tracking parameters on your device (utm_…, fbclid, gclid, mc_eid and many others) and unwraps redirect links that contain their destination (Outlook Safe Links, Google, Proofpoint). The list of rules is updated from our server; the cleaning itself needs no connection.
Paid services. Some links do not say where they lead (URL shorteners, bulk-mail tracking links). On request, our server follows them to show you their destination, without opening them in your browser. Likewise, the image proxy loads images on your behalf to hide your IP address from the sender, and strips their metadata. Neither link addresses nor image addresses are logged. These services are not on sale yet.
The Hexomail account
Hexomail works without an account. The optional Hexomail account is used for HexoTransfert and for syncing between your devices. You create it with one of your email addresses, verified by a code that Hexomail reads on its own in your inbox, and a password.
Sync. Your accounts (without passwords), signatures, trusted domains and settings are encrypted with AES-256-GCM on your device, using a key derived from your HexoTransfert key, which we do not have. Our server stores unreadable blocks; it sees how many there are, their size and when they were last updated.
New device. Scan the QR code shown by a device that is already set up, or enter its short code, then check that the same verification code appears on both screens. Your accounts, passwords included, move from one device to the other in an envelope encrypted for the new device only; our server relays it without being able to open it and deletes it as soon as it is received, after 10 minutes at most. Google access is not transferred: each device signs in to Google itself.
If you lose a device
You still have another device. Add the new one by scanning the QR code of the remaining one: everything is transferred, including your HexoTransfert key.
You have lost all your devices. Your messages are still with your provider: reinstall Hexomail and add your addresses. You sign back in to your Hexomail account with your password and create a new HexoTransfert key; each of your addresses receives an alert email. HexoTransfert files received with the old key and synced data can no longer be opened.
This is deliberate: your Hexomail password cannot recover your key, otherwise anyone who found it out (or we ourselves) could read your files. If a key is replaced on one of your devices, the old one remains usable on the others to open old files, and can be transferred to them.
HexoTransfert
HexoTransfert sends a file that only its recipient can open. The file is encrypted on your device and then attached to an ordinary email: it never goes through our servers and is never stored there.
The recipient must use Hexomail and have published their key. Hexomail finds it in our directory from their address; a key can only be published for an address whose owner has proved that they read it, with a code received by email. If the recipient has no key, the transfer is not possible.
| Role | Algorithms |
|---|---|
| Key exchange | X25519 and ML-KEM-768 (FIPS 203), combined with HKDF-SHA256 |
| File encryption | AES-256-GCM, after compression |
| Signature | Ed25519 and ML-DSA-65 (FIPS 204), both of which must be valid |
Each role combines a proven algorithm with an algorithm standardised in 2024 to resist quantum computers: both would have to be broken. The file carries the sender's public key and the signature of its content. Keys are provided by our directory: a compromised directory could in theory provide a fake key. The safeguard is the key fingerprint, shown in each person's HexoTransfert settings: for a sensitive exchange, compare it with your correspondent through another channel (phone, in person). The HexoTransfert format will be published as open source.
The web version
Open mail.hexonest.fr/app on any computer: your inbox appears, served by your usual phone or computer. The web version is not an email client. Your device is what fetches and sends your messages, with its own settings and passwords; the browser displays what the device sends it. You therefore need the Hexomail app on a device that is switched on and connected to the Internet and to your Hexomail account.
Signing in. The page shows a QR code and a short code. In the app, open Settings, Devices, “Access from a browser”, then scan the QR code or enter the code. Both screens then show the same six-digit verification code: if it differs, refuse, someone is in the middle. You then authorise the session on your device, with full or read-only access.
End-to-end encrypted. The browser and your device agree on a key known only to them, which our server does not know. Our server relays encrypted blocks: it sees IP addresses, the time and the size of the exchanges, never their content. It stores neither the code displayed nor the exchanges. A block that is modified, deleted or replayed on the way ends the session.
| Role | Algorithms |
|---|---|
| Key exchange | X25519 and ML-KEM-768 (FIPS 203), combined with HKDF-SHA256 |
| Traffic encryption | AES-256-GCM, one key per direction, numbered messages, key renewed every 10,000 messages |
| Against interception | Key fingerprint in the QR code and verification code shown on both screens |
Nothing stays on the computer. Displayed messages stay in the page's memory: no cookies, no local storage, no message cache. The page only caches its own files. When you sign out, the page reloads to clear its memory.
End of session. The session ends when you close the tab or sign out, when you revoke it from your device, after fifteen minutes of inactivity, and after twelve hours at the latest. Your device serves only one web session at a time.
What is prepared on your device. Before sending a message to the browser, your device removes its scripts and blocks remote images: the web version never displays a remote image. Links are cleaned and ask for confirmation before opening, as in the app. Sending attachments from the browser is not possible yet.
Gmail. Gmail accounts connected with Google are not accessible from the web version: your device does not pass them on to it. They remain available in the app.
The limit of a web page. The code of the web version is served by our website, and it is this code that decrypts your messages in the browser. A modified version of this code, by us or by someone who had taken control of the website, could therefore read the messages displayed. This is the limit of any encrypted messaging used in a browser, and the reason why the web version is less protected than the apps. To make it verifiable, each version is built reproducibly: the page displays the fingerprint of its version, the list of fingerprints of each of its files is published at mail.hexonest.fr/app/empreintes.txt, and we check that the files served are exactly those built from our code.
The computer's browser and operating system remain outside our control: only open the web version on a computer you trust, and prefer the app for sensitive exchanges.
Mailing lists
Hexonest hosts mailing lists (newsletters) for organisations. This is the only exception to the principle of this page: the addresses of subscribers, who are third parties, are stored on our servers, in France.
Who manages them. A list is created by Hexonest for an organisation, which grants access to one or more Hexomail accounts. These accounts manage subscribers from the app: adding, importing, unsubscribing, erasing, exporting. The organisation is the data controller; Hexonest acts as a processor (Article 28 GDPR).
How it is protected. Subscribers' addresses and names are encrypted with AES-256-GCM in the database of the list service, separate from the one for accounts and keys. A non-reversible fingerprint makes it possible to spot a duplicate or an unsubscribed person without decrypting. For each subscriber, proof of their consent is kept: date, sign-up channel, declared origin, and IP address for the public form, where sign-up goes through a double opt-in.
Sending. A newsletter goes out from the sender's email account, from the app: one copy per subscriber, never a list in copy, with one-click unsubscribe headers. The app fetches the addresses for the duration of the send, without keeping them; the content of the newsletter does not go through our servers. A bulk sending service run by Hexonest is planned; if it opens, this page will say what then goes through our servers.
Unsubscribing. Every message contains an unsubscribe link that always works. An unsubscribed person can no longer be re-subscribed by an import: all we keep is a non-reversible fingerprint of their address, so as never to write to them again. The rules imposed on senders are in the terms of use.
Report a vulnerability
Think you have found a security vulnerability in Hexomail, HexoTransfert or our servers? Write to bonjour@hexonest.fr with “Sécurité” (Security) in the subject line, and give us time to fix it before making it public. We will reply and keep you informed of the fix.
Frequently asked questions
Can Hexonest read my email?
Your messages do not go through our servers, so we never receive them. Your email provider, on the other hand, stores them and can read them, just as it does today: Hexomail does not encrypt your email.
Does Hexomail work offline?
Yes, for reading and searching messages already fetched. Attachments are downloaded when you open them.
How much does it cost?
The app is free. The optional online services (image proxy, revealing where opaque links lead, HexoTransfert key lookups beyond the free credits) will be paid; they are not on sale yet.
Is Hexomail open source?
No. The HexoTransfert format will be published as open source.
Where are your servers?
At OVH, in Gravelines, France. Verification codes and alerts are sent from our mail server, hosted by HostNatPro, in France.
Why does Google show “unverified app”?
To access Gmail, an app must be verified by Google. Hexomail's has not been yet: when you sign in, Google shows a warning, and the number of Gmail accounts that can connect is limited. You can continue with full knowledge of the facts, or add your Gmail account with an app password.
What does my email provider see?
Everything it already saw: your messages, your contacts and your devices' connections. Hexomail does not encrypt your email and does not hide it from your provider; it protects you from senders who track you.
Why not Thunderbird?
If Thunderbird suits you, keep it: it is a very good free and open-source client. Hexomail makes different choices: active protections with no setup (trackers flagged, links cleaned before opening), the same app on computer and Android, encrypted sync of your accounts, and HexoTransfert.
Who is behind Hexomail?
Hexonest, a French simplified joint-stock company (SAS) based in Paris (see the legal notice).
Is the web version as secure as the app?
No, slightly less: exchanges are end-to-end encrypted and nothing stays on the computer, but the code that displays your messages is served by our website on each visit. See The web version.
Has the code been audited?
Not yet: no external security audit has been carried out to date. Publishing the HexoTransfert format will allow anyone to examine it.