Mail security that doesn't meter your mailboxes.
A protocol-aware mail proxy, a staged spam classifier, and click-time URL protection, all running on hardware you already own. No per-mailbox licence, no platform lock-in, and no message content leaving your network.
What it is
Most mail security is sold as a cloud subscription billed per mailbox, and it works by routing your mail through someone else's infrastructure. That is a poor fit for anyone with a sovereignty requirement, anyone deliberately off Microsoft 365, and any provider whose margin is being eaten by a per-seat fee they don't control.
This is the same capability built to run entirely inside your perimeter: a protocol proxy at the edge, a staged classifier behind it, and intent models for the cases that need reading rather than scoring. It drops in beside an existing rspamd installation, and it can run in observe-only mode first, scoring live mail at zero weight so you can see what it would have done before it decides anything.
The components
Scorpion, the mail protocol proxy
In productionOne protocol-aware entry point, decoupling the outside world from your mail backends. Backends can move, multiply, or be replaced without anything external changing. It is dual-stack on both sides, so it doubles as a bidirectional IPv6 to IPv4 gateway, letting an IPv6 mandate be met at the edge instead of by rebuilding every mail server behind it.
PDMSC, the staged classifier
In productionNine models arranged as a cascade, each able to decide or defer. Cheap, precise layers run first and most mail is settled early; the expensive layers only see what survives. The on-disk format is structural, so additional language sets and site-tuned models load alongside the general ones.
INTENT2, message intent classification
In productionA local language model reads what a message is actually trying to get the recipient to do, for the residue the cascade will not call. It runs on your own host; nothing is sent to an external API.
URL protection at click time
In testingBuilt into the proxy rather than bolted on beside it. Links are rewritten as the message passes through and adjudicated at the moment the recipient retrieves them, catching sites that are clean at delivery and weaponised an hour later. It fails open to the original link by design, and the rewritten links carry your own domain rather than a vendor's.
MISUIC, the URL intent classifier
In testingClassifies what a link is actually for, so a URL is judged on intent rather than on whether it has been reported before. This is what gives the click-time proxy a verdict on links no blocklist has seen.
Why this rather than the incumbents
Your mail never leaves your network
Classification and intent analysis both run locally. There is no vendor copy of your message bodies, no click telemetry leaving the building, and nothing to renegotiate when a data residency rule changes.
Priced per deployment, not per seat
Adding users does not add cost. For a provider reselling mailboxes, that turns a variable fee that scales against you into a fixed one.
One entry point, any backend
Backends can be migrated, consolidated, or replaced behind the proxy without touching MX records or client configuration. It is a migration tool as much as a security control.
Link protection without the platform
Click-time URL adjudication is otherwise bundled into Microsoft 365 or sold as a per-seat add-on. Here it is part of the proxy you already run.
Runs where you already run
- Systems
- FreeBSD, OpenBSD, BSDSUniX, Linux, Solaris 10
- Architectures
- AMD64, Intel, ARM64, SPARC64
- Hosting
- Bare metal, VMs, and logical domains
- Classifier
- 1.37 GB resident, 557 MB on disk (English set)
Figures are for the classifier backend, measured on the production deployment. The proxy is sized by connection volume and specified separately.
Who builds it
Built by Michelle Sullivan, who founded and ran SORBS, one of the longest-running anti-spam blocklists in the business. This is the engine that came after it: the same problem, approached without the assumption that mail security has to be someone else's cloud.
Taking on design partners
We are working with a small number of organisations to put this into production alongside their existing filtering. If you run your own mail, or run it for other people, we would like to hear from you.
- Mail providers and MSPs paying per mailbox for filtering they cannot tune.
- Organisations that cannot route mail through a foreign cloud.
- Anyone who needs IPv6 at the edge without rebuilding the servers behind it.