Filtering that stays inside the perimeter.
Klar Pro is a Postfix milter. It scores every message before delivery, on hardware you already operate, so customer correspondence never reaches a vendor's cloud.
Talk to usA cloud filter is an ICT third party, and DORA counts them.
Since 17 January 2025, DORA has applied. A cloud email filter is an ICT service under art. 3(21), supplied by an ICT third-party service provider under art. 3(19), and that is not a borderline reading. Every such contract belongs in your register of information (art. 28(3)) and has to carry the minimum contractual terms of art. 30(2), whether or not the function is critical or important. Where it is, exit strategies (art. 28(8)) and audit and access rights (art. 30(3)(e)) come on top.
None of that makes cloud filtering unlawful. It makes it administered, and the administration grows with what the vendor touches. Klar does not zero your obligations either: buy it and we are a supplier like any other. What changes is the thing underneath. No third party processes your customers' mail, because the classifier runs in your own SMTP path.
Regulation (EU) 2022/2554 (DORA)The classifier, in your SMTP path.
Klar Pro is a Postfix milter wrapping the same classifier that ships in the Mac app. It scores each message before delivery: spam is filed to Junk, and in reject mode the clearest spam is refused at SMTP time. The engine is AGPLv3, so your security team can read exactly what it does before it goes near a mail flow.
The part of Klar that reads your mail is an Apple-sandboxed Mail extension shipped without the network entitlement. It is not that we promise not to send your mail anywhere. It is that macOS refuses the connection, because the permission was never requested. Classification happens on your Mac, instantly.
What that means in practice
- No network access
- The free App Store app and its Mail extension ship without the network entitlement. macOS refuses any connection they try to open. This is a permission the app does not hold, not a policy it promises to follow.
- The model ships with the app
- The classifier is a multilingual transformer inside the app bundle. Nothing is fetched when a message arrives, so it works the same on a train as it does in the office.
- No account
- There is nothing to sign up for and no licence server the free app calls. Unless you contact us or choose to send an Email report, we do not know who you are.
- The engine is open source
- The scoring engine is AGPLv3. Your IT people do not have to take our word for any of this. They can read it, build it, and watch what it does.
Questions your compliance officer will ask
Is it production ready?
Not as a supported product you can buy and deploy tomorrow. The milter is built, passes its suite, including replay and stress runs, and installs with one command on Linux, but we are rolling out the commercial offer with design partners rather than selling it off the shelf. If you need turnkey this quarter, we are not it. If you want to shape it, this is the moment.
Where does it sit relative to our existing gateway?
In the SMTP path as a milter, behind whatever authenticates your mail. Klar reads the Authentication-Results header that your DKIM, SPF and DMARC checks already stamped rather than verifying them itself, so it has to run after them, not instead of them.
Does filtering send anything off the machine?
No. The free App Store app and its Mail extension have no network permission. If you choose Email report, Klar opens an editable draft in your own mail app; nothing leaves until you send it. Do not include confidential correspondence unless you are authorised to share it. Klar Plus, the paid companion you install yourself, separately uses the network for its licence, model and version checks. None carries your mail. The full list is on the local-first page.
Do we need a data processing agreement with you?
That is a question for your own counsel, and it depends on which part of Klar you run. Routine filtering sends us nothing. A user who sends an Email report may share selected messages, diagnostics and a removable monthly usage summary; our privacy policy explains what we then hold. Decide whether staff may use that report action with confidential correspondence.
What we are not claiming.
We are not offering legal advice, and a spam filter does not make anyone compliant. Your obligations are yours, and your bar, your regulator or your DPO is the right place to test them. What we can tell you is exactly where the software runs and what it is permitted to do, which is the part most vendors leave you to infer.
We are also not claiming perfect filtering. No filter is, and any vendor quoting you a single accuracy number is quoting a number from their corpus, not your inbox. What we will say is that being wrong about a message on your Mac and being wrong about it on someone else's server are not the same kind of wrong.
Read the whole local-first argumentRun it on your own mail servers.
Klar Pro is the Klar engine as a milter for Postfix and Stalwart. The open-source milter installs with one command; Klar Pro, the commercial licence for running it in a business, we are rolling out with design partners. If that fits how you buy, we should talk.