The second lock. While legacy mail protocols are off, a sign-in over IMAP,
POP3, ManageSieve or SMTP AUTH is refused for every account, so a listener
that exists by mistake -- or submission, which the SMTP lock keeps open --
still lets nobody in.
The check sits at the top of each protocol's sign-in, before the
credentials are looked at. So the answer is the same for a right password,
a wrong one and an account that doesn't exist; it isn't auth.failed, so it
counts nothing against the account and never feeds the auto-ban; and the
session stays open, since the mail app is being told, not thrown off.
Mail apps read the spec's words (LP-12, at server scope):
IMAP NO [ALERT] This server allows only INBUXA webmail and JMAP
apps. This mail app can't sign in.
POP3 -ERR [AUTH] ...the same...
ManageSieve NO "This server allows only INBUXA webmail and JMAP apps."
SMTP 535 5.7.0 This server allows only INBUXA webmail and JMAP
apps. This mail app can't send.
SMTP AUTH is refused on every SMTP listener, port 25 included: only mail
apps authenticate, so inbound delivery is untouched. LMTP is left alone.
The policy is read from the store on each sign-in rather than cached, so
every node of a cluster answers the same the moment the switch turns.
Each refusal raises a new event, auth.legacy-protocol-refused (id 642, info
level, also in the packaged schema), with the protocol as source, the
policy's scope and the domain -- never the account. The session adds the
listener and remote IP.
tests/e2e/legacy_protocols.py now also proves, on a running server: a
normal IMAP and submission sign-in works with the switch on, before and
after; while off, submission refuses the right password and six wrong ones
with the same words and without hanging up; and an IMAP listener created by
mistake while off refuses the right password, a wrong one and an account
that doesn't exist. All 33 checks pass. SMTP sign-ins in the script wait
out a second first: every connection arrives from Docker's gateway, and the
stock inbound throttle takes five a second from one IP.
A complete mail and collaboration server, every feature included, under the AGPL
INBUXA is a mail and collaboration server: JMAP, IMAP, POP3, SMTP, CalDAV, CardDAV and WebDAV, in one Rust binary, with ihasmail as its web front end. It is a fork of Stalwart. Project site: inbuxa.org. Documentation: docs.inbuxa.org.
Stalwart ships some features only in a paid Enterprise Edition: multi-tenancy, masked email, undelete and others. INBUXA ships everything to everybody under the AGPL-3.0, rebuilding those features independently and without using any of Stalwart's Enterprise code.
What's different from Stalwart
- Every feature, one edition. No license key, no edition checks, no
upsell. See
docs/spec/SPEC.md§4 for the features being rebuilt, anddocs/spec/features/for each one's specification. - Webmail and administration by ihasmail, as a separate service that can run beside the server or elsewhere. Stalwart's own web interface is removed, so there's no web front end on the mail host.
- Clean-room rebuilds. Enterprise-only code is stripped from every
upstream release before it's imported. The rebuilt features are written
from specifications that use only public sources (
docs/spec/SPEC.md§3).
How the fork is kept
Upstream releases arrive as stripped snapshots, never with upstream's git
history, which contains Enterprise code. tools/fork/strip.py builds each
snapshot on top of upstream's own ossify.py, then verifies it independently.
The report for every import is in docs/fork/strip-reports/. See
docs/spec/SPEC.md §2.
Building
cargo build --release -p inbuxa # the binary is target/release/inbuxa
docker build -t inbuxa . # or the container image
Settings are read from INBUXA_* environment variables. An existing Stalwart
install's STALWART_* variables still work, with a warning to rename them.
New installs keep their data in /var/lib/inbuxa and logs in
/var/log/inbuxa. Existing installs keep the paths their configuration
already names, so none of their data moves.
License and credits
INBUXA is free software under the GNU Affero General Public License, version 3.
It is a fork of Stalwart, copyright © Stalwart Labs LLC, modified by Coffey Labs in 2026. Upstream's copyright notices are kept on every file they cover, and every upstream file this fork changed says so in its header, under the notice it came with. Stalwart's files are dual-licensed AGPL-3.0-only or Stalwart's Enterprise License, and INBUXA takes them under the AGPL-3.0 only. A few of those files also carry code from other projects under MIT or BSD licenses, which stays under those licenses; THIRD-PARTY.md lists it with its notices. "Stalwart" is Stalwart Labs' name. INBUXA isn't affiliated with or endorsed by Stalwart Labs.
The INBUXA mark reuses ihasmail's cat-and-envelope artwork.