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Folders, search, type-ahead contacts
Traditional folders — Inbox, Sent, Draft, Starred, Archive, Trash. The composer has To/Cc/Bcc with type-ahead contact suggestions. Global search across subject, sender and body.
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Application · uMail
Mail.
Encrypted by default.
Encrypted email
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Capabilities
What you can do with uMail.
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Encrypted attachments and replies
Drag-and-drop attachments, threaded replies, full quoting. Every message and attachment is encrypted on your device before it reaches the server.
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Zero-knowledge mail by default
The server only ever stores opaque ciphertext. We cannot read your mail — no matter who asks. Passphrase-based authentication means no password database to leak.
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Protection
Security for uMail.
Content in uMail is inside the end-to-end encrypted envelope: it is encrypted in your browser before it is transmitted, and the server stores ciphertext it holds no key for.
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Post-quantum cryptography by default
All authentication and key exchange uses NIST-standardized ML-DSA-65 (FIPS 204) signatures and ML-KEM-768 (FIPS 203) key encapsulation. There is zero RSA, zero elliptic-curve, zero classical-only crypto in the authentication path. Defeats store-now-decrypt-later attacks.
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End-to-end encryption on your device
Every payload is encrypted in your browser using XChaCha20-Poly1305 (RFC 8439) with a 192-bit nonce and a Poly1305 authentication tag. The plaintext exists only in your tab's memory. When you close the tab, the plaintext is gone.
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The server holds ciphertext it cannot open
For uMail content the server only ever stores ciphertext and public keys. It cannot decrypt your data — by architecture, not by promise: there is no backdoor, no master key and no key escrow, because no key that would open it ever reaches the server.
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Your keys stay on your device
Your private keys are derived in your browser from three secrets only you control, and are held in memory for the session only — never written to browser storage, never sent to the server. A new device derives the same keys locally from the same three secrets.
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Mechanics
How uMail works.
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Open uMail in your browser
UltimaOS runs in any modern browser — Chrome, Firefox, Safari, Edge. Nothing to install. Sign in by re-entering the three secrets your keys are derived from, and the same keys are rebuilt locally on whatever device you are using.
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Your data is encrypted before it leaves your device
Sending a message, uploading a file, writing a note — the content is encrypted with XChaCha20-Poly1305 and authenticated with an ML-DSA-65 signature before any byte crosses the network boundary.
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The server stores ciphertext and returns it on demand
The server keeps an opaque blob it has no key for. When you open uMail, those blobs are streamed to your device, decrypted locally and rendered. Plaintext exists only in your tab.
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04
Changes follow you across devices
Any change you make is uploaded and picked up by every other device you are signed in on, so uMail looks the same wherever you open it.
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Inside the suite
How uMail fits in the suite.
01
Contacts
Type-ahead contact suggestions in the To/Cc/Bcc fields. Each contact's address is encrypted to your key.
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Calendar
Mail invites become Calendar events with one tap. Reminders fire from your device, not the server.
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Files
Drag attachments into the composer. Files encrypts and streams them to recipients.
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Tasks
Convert any mail thread into a task list. Tasks inherits the thread's participants and encryption.
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Get started
Get started with uMail.
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01
Open uMail in your browser
UltimaOS runs in Chrome, Firefox, Safari and Edge. Nothing to install. Sign in with your passphrase to derive your private key locally.
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Open the workspace and launch uMail
The launcher shows every app. uMail is right there with its capsule video preview. Click to open.
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Connect it with the rest of the suite
uMail works alone, but it shines when combined with the rest of the UltimaOS apps. Same identity, same workspace, one place to work.
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Frequently asked
Questions about uMail.
Is uMail end-to-end encrypted?
Short answer
Yes. All content in uMail is encrypted in your browser using XChaCha20-Poly1305 with a fresh key per item. The UltimaOS server only ever stores ciphertext and public keys — it cannot decrypt your data, no matter who asks.
What cryptography does uMail use?
Short answer
uMail uses the same post-quantum stack as every other UltimaOS app: ML-DSA-65 (FIPS 204) for authentication, ML-KEM-768 (FIPS 203) for key encapsulation, XChaCha20-Poly1305 (RFC 8439) for symmetric encryption, and HKDF-SHA256 for key derivation.
Can I use uMail on multiple devices?
Short answer
Yes. Sign in on any device by re-entering your three secrets and the same keys are derived locally, so your uMail content follows you. Changes sync live across all signed-in devices.
Is uMail GDPR-compliant?
Short answer
Yes. UltimaOS is built and operated in the European Union by an EU company. The architecture is GDPR-compliant by design — encrypted data, EU-only infrastructure, no US CLOUD Act exposure, no advertising, no third-party trackers. See the GDPR page for the full breakdown.
How much does uMail cost?
Short answer
UltimaOS is free for individuals and families — permanently, not as a trial. Organizations pay per seat once early access ends, and that is what funds the free accounts. There is no per-app add-on.
Can I export my uMail data?
Short answer
Yes. UltimaOS supports encrypted export of all your content for backup and portability. The export is encrypted to a key you control; you can store it on your own infrastructure or in a personal encrypted backup.
Can I use uMail with my existing email address?
Short answer
uMail works as a standalone encrypted mail client inside UltimaOS. Bridging to external mail providers (IMAP/SMTP) is on the roadmap for a future release — with the caveat that external providers cannot read your encrypted mail.
Does uMail support PGP / S/MIME?
Short answer
uMail does not need PGP or S/MIME because every message is already end-to-end encrypted at the protocol level. There is no public key to distribute, no certificate authority to trust — encryption is the default.