One server. One program to install. No stack to assemble.

A real mail and collaboration server. Not a demo, not a teaser.

Everything below runs in the single binary. The web client and the desktop sync agent come with it.

• MailJMAP Mail (RFC 8621) plus IMAP4rev2 over TLS. SMTP inbound and outbound. Server-side Sieve filtering with a from-scratch interpreter, managed over ManageSieve.
• Calendar, contacts, tasksJMAP Calendar, Contacts (RFC 9610) and Tasks, with CalDAV and CardDAV for legacy clients — Thunderbird, Apple Mail, eM Client. ICS import and export.
• Files and sharingA file tree with version history, a trash, and share links your server issues and can revoke. Shared with colleagues by principal or by group, or mounted as a network drive on the office LAN.
• NotesNotebooks, pages and labels for what is not a task: a call summary, an idea, the points from a meeting. Pages link to a message, a contact, an appointment or a file, are found by full-text search, and a notebook is shared like a calendar — read, write or administer.
• Chat and callsRooms, polls, read receipts and drafts that follow you between devices. Video calls between up to three participants, with screen sharing, a waiting room, and a link that lets someone without an account join.
• Shared mailboxes and team addressesA team gets its own address and mailbox, activated from the client, visible in IMAP clients too. Delegated access to someone else’s mail is logged, and a departure is handled in one command.
• Spam filtering, built inA scored three-stage pipeline: network checks (SPF, DKIM, DMARC, ARC, DNSBL), then content analysis, then per-tenant Bayesian classification and URL inspection. Phishing is scored apart from advertising, and a message that claims to be from a bank without anything that belongs to it is caught. No rspamd, no SpamAssassin, no third-party API keys.
• Mail and relay server in oneSend through any relay from day one when your IP is new or port 25 is blocked, then go direct. Or run the box as a smarthost for other servers and for your emailing tools: domains proven by DNS, a gradual ramp per sender, your people’s mail always ahead of the campaigns, and relayed mail erased once delivered.
• Disk encryption, verified + passkeysEncryption at rest is your disk’s: the installer measures the data volume and refuses a plaintext one without your explicit consent. Secrets stay under a per-tenant key hierarchy that never leaves your infrastructure. Phishing-resistant passkey sign-in over WebAuthn. Post-quantum key exchange on every TLS port.
• Audit trail and data-access logA hash-chained, tamper-evident audit log you can verify and attest from the command line, plus an opt-in log of who accessed whose data. A legal hold freezes an account’s mail against any destruction, and the GDPR erasure workflow leaves a proof.
• Legacy protocol supportIMAP, CalDAV and CardDAV translation so existing desktop and mobile clients connect unchanged while you move to JMAP at your own pace.
• Fail-loud integrityNo silently dropped mail, no swallowed errors. Any message accepted with a 250 is delivered or quarantined — never to /dev/null. A write the server does not understand is refused by name, never answered with a false “saved”.

One binary. SQLite. Up to about 2000 accounts.

OxiMail is SQLite-backed and has been validated to around 2000 accounts per instance — far beyond what a five-user deployment needs, and enough for a cooperative, an association or a small institution when you outgrow the free tier. Put it on a Debian host, point your DNS, and you have a full mail and collaboration server in one process, one config, one login. No JVM, no orchestration, no specialist on call to keep a six-service stack standing.

# Debian 13, 2 GB of RAM, a domain and a public IP
# one binary, one config file, one systemd service
# no Postfix, no Dovecot, no web server alongside it

The operator documentation covers the whole path: requirements, ports, first boot, DNS and DKIM, TLS, migration from your current server. Prebuilt packages arrive with the public source release — until then, tell us and we will get you a build.

Fair source: free below the line, paid above it, and AGPL for everyone after four years.

• Running OxiMail for your own organisation, five users or fewer: free, the whole suite.
• Above five, or operating it for someone else: a paid licence, from the first mailbox.
• Every release becomes AGPL-3.0-or-later four years after it ships — automatically, a ceiling on our own pricing power.

See what free includes and what is paid →