Eon Phoenix

Post-quantum mail. Free, and yours to read the source of.

Eon Phoenix is a mail client that speaks ordinary IMAP and SMTP and seals what it sends, so the mail server carries your correspondence without being able to read it. It is free and the source is public. There is no licence to buy, no seat count, and no account with us.

Download Source on GitLab

Three kinds of message, one inbox

Email. Ordinary correspondence over IMAP and SMTP, to anyone with an address. Sealed when the other side can be sealed to, plain when it cannot — and the client says which it was.
C-Mail. Confidential Mail: the same mail, in the same shape, that only ever goes out sealed. If the recipient publishes no key there is nothing to fall back to, so it is not sent — a confidential message is never quietly downgraded to a plain one.
D-Mail. Discrete Mail: an always-encrypted, chat-shaped conversation that rides on the same email address. It appears as a thread rather than a list of messages, and it never leaves the encrypted path.

What the server never sees

Every protected message is sealed twice over. A post-quantum key encapsulation and X25519 both have to be broken before the body can be read, and the body itself is AES-256-GCM. Signing is ML-DSA-87 alongside Ed25519, applied before encryption, so a message that arrives is both unreadable in transit and attributable on arrival.

An identity does not carry one key. It publishes a set — ML-KEM-1024 and FrodoKEM-1344-SHAKE, each paired with X25519 — and the sender picks the strongest algorithm the recipient also publishes. Two families rather than one, so a break in either leaves the other standing.

Finding somebody's key

Codex is the directory that makes this work across domains: one keyserver per domain, publishing the key sets of the addresses it is responsible for. A client looks up the recipient's domain, fetches the set, and seals to it. No central registry, and no key exchange over the side channel that people actually use, which is the bit that has always broken PGP.

Where it runs

Desktop. macOS, Windows and Linux. Go with a web frontend, built as one native binary.
Codex. A server you run for your own domain, or a domain that runs one for you.

Free and open source

Phoenix was a closed beta with per-tester access codes. It is not any more: the builds and the source are public, and the releases live on GitLab. What we ask in return is what any project asks — report what breaks, and say what you needed and did not find.

Partners we are looking for

The client being free does not mean there is nothing to build on. Four kinds of partner, and each of them owns a piece we do not:

Mail and hosting providers. You run Codex for the domains you already host, and key discovery works for your users without any of them having to do anything about it.
Managed service providers and resellers. You roll Phoenix out across a client estate, keep it running, and charge for that. The software costs nothing; the work around it is worth paying for.
Software vendors and integrators. You want the sealing layer or D-Mail inside a product of your own. That conversation is about interfaces, and it is one we would rather have before you have built around a guess.
Packagers. Distribution repositories, internal app stores, managed device fleets — anywhere a build has to arrive through a channel that is not a download page.

What a partner gets from us: builds before they are announced, a direct line to the people who wrote the code, and a say in what the next release has to carry. Commercial terms depend on which of the four you are, so that part is a conversation rather than a price list. Get in touch and say what you have in mind.

Facts

pricefree, and the source is public

signingML-DSA-87 (FIPS 204) + Ed25519, sign-then-encrypt

key exchangeML-KEM-1024 (FIPS 203) and FrodoKEM-1344-SHAKE, each hybrid with X25519

bodyAES-256-GCM

transportordinary IMAP and SMTP; no bespoke server

directoryCodex, one keyserver per domain

platformsmacOS · Windows · Linux

releasesGitLab

Download Phoenix Talk about partnering

Eon Phoenix — post-quantum end-to-end encrypted mail client with C-Mail and D-Mail conversations, plus Codex, a per-domain directory keyserver for key discovery. Transport is unmodified IMAP/SMTP. A desktop client (Go backend, web frontend) for macOS, Windows and Linux, built as one native binary. Free and open source; releases and source on GitLab. Partnership enquiries via /contact.html.

Message kinds

emailIMAP/SMTP to any address; sealed when the recipient publishes a key, plain when not, stated per message

C-MailConfidential Mail — mail-shaped, sealed without exception; no key published means the message is refused, never downgraded

D-MailDiscrete Mail — always-encrypted chat-shaped thread on the same address

Cryptography

identityML-DSA-87 (FIPS 204) + Ed25519 — fixed; defines the fingerprint

kem setML-KEM-1024 (FIPS 203) and FrodoKEM-1344-SHAKE, each paired with X25519

selectionsender picks the strongest algorithm the recipient publishes as active; family diversity ranks above security level

bodyAES-256-GCM

ordersign-then-encrypt

Distribution

licencefree and open source

sourceGitLab

releasesGitLab releases, per platform

platformsdarwin amd64/arm64 · linux amd64 · windows amd64

directoryCodex, one keyserver per domain, self-hosted

partnersmail/hosting providers (run Codex) · MSPs and resellers (deploy and support) · vendors and integrators (embed the sealing layer or D-Mail) · packagers (distro repos, internal stores, managed fleets)

partner termsper kind, not a price list; early builds and roadmap input in every case

enquiries/contact.html

Documentation

Full reference at docs.eoncore.eu/eon-phoenix/. Every page there is also Markdown: append index.md to its URL. All products in one file: docs.eoncore.eu/llms-full.txt.