Contribute · train the filter
Contribute by forwarding
Klar is free, and you can help make it smarter without paying a cent or installing anything. Set up one filter rule that auto-forwards spam to spam@klar.im, and every junk message that lands in your inbox becomes a training example that sharpens the filter for everyone.
Why it works
Klar's spam model learns from real, recent spam. The more varied the examples, the better it gets at catching what's circulating right now. Your forwarded junk feeds that loop directly. No payment, no install, no account.
Redirect vs. forward: pick redirect if you can
Two ways to send mail on: redirect (also called "resend" or Sieve redirect) preserves the original sender and headers, so the message arrives exactly as the spammer sent it. Plain forward wraps the message and rewrites the sender, which strips signal. Redirect gives the cleaner training example, so prefer it where your provider offers it.
Where true redirect is available:
- Redirect: Apple Mail (Redirect), Outlook desktop (Redirect), Fastmail / generic Sieve (
redirect) - Forward: Gmail, iCloud web, Proton, Outlook web: forward only. Still useful; forward away.
Set up a rule for your provider
Gmail
Gmail forwards (no true redirect). You must verify the destination first: Settings → See all settings → Forwarding and POP/IMAP → Add a forwarding address → enter spam@klar.im. Gmail emails a confirmation link to that address; until we confirm it on our side, every Gmail forward rule silently fails (see Heads-up below). Once verified: Settings → Filters and Blocked Addresses → Create a new filter → set a condition (e.g. label:spam or your own criteria) → Create filter → tick "Forward it to" and choose spam@klar.im. Note: Gmail filters don't run on mail Google already auto-sorted into Spam, so either forward from a label you control or accept that auto-Spam won't be covered.
Apple Mail / iCloud
Mail.app (Mac): Mail → Settings → Rules → Add Rule → set your condition → Perform actions → choose Redirect Message (preserves the original) → enter spam@klar.im. Mail rules only run while Mail is open on that Mac. iCloud web: iCloud Mail → Settings (gear) → Rules → Add a Rule → set the condition → "Forward to" spam@klar.im. This runs on Apple's servers, always on.
Proton Mail
Proton's auto-forward and Sieve filters are a paid-plan feature; free accounts can't auto-forward. Paid plans: Settings → All settings → Filters → Add filter (or Add sieve filter for a redirect) → match on your spam criteria → action: forward to spam@klar.im. Free plan: there's no auto-forward, but you can still help by forwarding spam manually from the message menu.
Outlook / Microsoft 365
Outlook on the web: Settings → Mail → Rules → Add new rule → name it → add a condition → add action "Forward to" → spam@klar.im → Save. Outlook desktop: Home → Rules → Manage Rules & Alerts → New Rule → pick your condition → choose redirect it to people (true redirect) or forward → spam@klar.im.
Fastmail
Settings → Filters & Rules → Create new rule → set the condition → action Redirect to spam@klar.im (Fastmail does a true redirect that keeps the original headers). For full control, Settings → Filters & Rules → Edit custom Sieve and use redirect "spam@klar.im";.
Generic IMAP / self-hosted (Sieve)
If your server runs Sieve (Dovecot Pigeonhole, Stalwart, etc.), add a rule that redirects matching mail. The redirect action preserves the original message and headers, the cleanest possible signal. Adjust the test below to whatever marks spam on your setup.
require ["fileinto"];
if header :contains "X-Spam-Flag" "YES" {
redirect "spam@klar.im";
}Heads-up for Gmail users
Gmail won't let you forward to an address it hasn't verified. When you add spam@klar.im as a forwarding address, Gmail sends a confirmation link there and we have to click it. If you set up a rule and nothing seems to arrive, the handshake hasn't completed yet. Give it a little time, and the forwards will start flowing once verification is done.
What we receive, and what we don't
We receive the spam you forward, nothing else. Not your inbox, not your contacts, not your legitimate mail. Only the messages you deliberately send to spam@klar.im.
Forwarded spam is used to build training examples and then aggregated. After aggregation the examples carry no identifier tying them back to you, so there is nothing user-unique left to retain.
Want something pulled before it's aggregated? Email support@klar.im and we'll remove it. See our Privacy Policy for the full picture.
Only forward real spam. Never forward private, personal, or legitimate mail. Once it's sent we can't know it shouldn't be there. If you're not sure a message is junk, don't forward it.
Spread the word
Helping privacy communities find this is itself a contribution. Here's a ready-to-paste post for r/degoogle, r/privacy, r/PrivacyGuides, or r/selfhosted:
You can train an open, EU-made spam filter for free, just add one forwarding rule
Klar is a free, privacy-respecting spam filter built in the EU. It learns from real spam, so the more varied junk it sees, the better it gets at catching what's actually circulating. You don't have to pay or install anything to help. Add one mail filter that auto-forwards (ideally *redirects*, to keep the original headers) spam to spam@klar.im, and every junk message that hits your inbox becomes a training example for everyone. Per-provider steps (Gmail, Apple Mail/iCloud, Proton, Outlook, Fastmail, generic Sieve), the redirect-vs-forward explanation, and exactly what they do and don't receive: https://klar.im/contribute Forward only real spam. Never private or legitimate mail.
Add a rule, train the filter
One filter rule. Every spam you'd have deleted anyway makes Klar smarter for everyone.
spam@klar.im