Spam filtering for your own mail server.

The Klar engine as a Postfix or SMTP milter, on infrastructure you control. Run it in any region you choose, and your mail never leaves your servers.

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Inline at your mail server

Klar runs as a milter in the SMTP path. It scores every message before delivery, so spam is rejected at the door instead of landing in mailboxes.

senders
Mail server Postfix · Stalwart
Klar milter, inline
Inbox
0 delivered 0 blocked before delivery
Runs in the SMTP path, before delivery. Spam is stopped in flight and never reaches a mailbox.
  1. 01

    Drops into Postfix

    Klar runs as a milter. Every inbound message is classified by the on-device engine and tagged with X-Klar headers. Your Sieve rules file spam to Junk.

  2. 02

    Stays on your infrastructure

    Classification runs where your mail already lives. Nothing is sent to a third party. That is the sovereignty cloud gateways cannot offer.

  3. 03

    Learns from your users

    When users move mail to or from Junk, Klar records the correction and adapts, on your servers, not ours.

Read the engine, run it yourself.

The Klar engine is open source under AGPLv3. Build it, audit it, and see exactly what runs on your servers. AGPLv3 means changes you ship have to stay open. If that does not fit your business, a commercial licence is available.

It ships with a reference Postfix milter today. A Stalwart milter is next, so the same engine drops into either mail server.

View the engine on GitHub

Early access

Self-hosted Klar is rolling out to design partners. Tell us about your setup and we will be in touch.

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