The landscape
Choosing a spam filter
The real differences are not in the marketing numbers. They are in where the filter runs, who gets to read your mail, and what it costs.
| Product | Runs on | Who can read your mail | Works with | Price |
|---|---|---|---|---|
| KlarOn-device AI filter | Your Mac | No one new. Your mail never leaves the device. | Apple Mail, with any account: IMAP, Gmail, iCloud, Exchange | Free forever |
| SpamSieveOn-device Bayesian filter | Your Mac | No one new. Processing stays on your Mac. | Apple Mail, Outlook and other Mac clients | $39.99 one-time |
| Klar fits better when Spam comes in several languages, or you don't want to train a filter | ||||
| SaneBoxCloud triage service | SaneBox's servers | SaneBox analyzes headers in its cloud; some features fetch message bodies | Any IMAP or Exchange account | From $4.99/month (2-year billing) |
| Klar fits better when Confidentiality matters: sorting without cloud access, marketing via Klar Plus (paid) | ||||
| GmailProvider's built-in filter | Google's servers | Google processes your mail to filter it | Gmail accounts | Included |
| Klar fits better when You read mail in Apple Mail, where Gmail's tabs don't carry over; marketing via Klar Plus (paid) | ||||
| Microsoft 365Provider's built-in filter (EOP) | Microsoft's cloud | Microsoft processes your mail to filter it | Microsoft 365 and Exchange Online mailboxes | Included |
| Klar fits better when You want a second, local pass you control, for work and personal accounts alike | ||||
| LibraesvaEnterprise email security gateway | Your organization's servers, or its cloud | Stays on your infrastructure when deployed on-premises | Your organization's mail flow, in front of the mail server | Enterprise quote |
| Klar fits better when You're an individual, or a small self-hosted server (Klar Pro milter) | ||||
| SpamAssassinOpen-source content filter | Your mail server | Runs on your own server. Mail stays on your infrastructure. | Server-side, in front of any mailbox (Postfix, Sendmail and other MTAs) | Free and open source |
| Klar fits better when You read mail in Apple Mail and don't run your own mail server | ||||
| RspamdOpen-source spam filtering system | Your mail server | Runs on your own server. Mail stays on your infrastructure. | Server-side, integrates with Postfix, Exim and other MTAs | Free and open source |
| Klar fits better when You read mail in Apple Mail and don't run your own mail server | ||||
| MailinblackCloud email security service | Mailinblack's cloud, or an on-premise gateway | Analyzes your organization's mail in its cloud to filter it | Your organization's mailboxes, in front of the mail server | Per-mailbox subscription (quote) |
| Klar fits better when You're an individual on Apple Mail, not an organization buying a managed gateway | ||||
| Leave Me AloneCloud inbox-cleaning service | Leave Me Alone's servers | Reads your mailbox in its cloud and stores subscription metadata | Gmail, Outlook and any IMAP mailbox | From $9/month, or a $19 one-time 7-day pass |
| Klar fits better when Spam is the problem: a filter that learns on your Mac, without giving a service access to your mailbox | ||||
| Clean EmailCloud bulk email cleaner | Clean Email's servers | Analyzes headers in its cloud; states it never downloads message bodies | Gmail, Yahoo, Outlook and any IMAP mailbox | From $7.99/month |
| Klar fits better when You want spam caught by a filter that learns, not by rules you write and maintain | ||||
| MailWasherDesktop spam filter for Windows | Your Windows PC | Previews mail on the server; junk is deleted before your mail program downloads it | POP and IMAP accounts, on Windows only | Free for one address; Pro from $49.95 |
| Klar fits better when You read mail on a Mac: MailWasher's own FAQ says it is Windows-only | ||||
Product and price details from the vendors' public pages, July 2026: c-command.com, sanebox.com, support.google.com, learn.microsoft.com, libraesva.com, spamassassin.apache.org, rspamd.com, mailinblack.com, leavemealone.com, clean.email, mailwasher.net. Klar is not affiliated with or endorsed by any vendor named here; names are used only to identify the products.
The honest picks
- SpamSieve
- A proven on-device filter with two decades of history. Pick it if you like Bayesian filtering you train yourself and want a mature indie tool. Klar takes a different bet on the model: a multilingual transformer instead of word statistics.
- SaneBox
- Not primarily a spam filter: it sorts your inbox by importance, in the cloud. Pick it if your problem is too much legitimate mail and you are comfortable giving a service access to your mailbox.
- Gmail
- Very good and included. If you live in Gmail's own apps and are fine with Google processing your mail, you may not need anything else. Klar earns its place when your accounts land in Apple Mail.
- Microsoft 365
- Exchange Online Protection is on for every Microsoft 365 mailbox and your admin manages it. On a work account, that decision is usually made for you. Klar still helps with what reaches Apple Mail.
- Libraesva
- An EU email security gateway for organizations that run their own mail: appliance, sandboxing, compliance tooling. It is not aimed at individuals.For a lightweight self-hosted layer, see Klar for servers.
- SpamAssassin
- The classic open-source filter: rules plus Bayesian scoring, two decades of deployment. Powerful once tuned, but it lives on a mail server you run and maintain, not on your Mac.For a lightweight self-hosted layer, see Klar for servers.
- Rspamd
- A fast, modern open-source filter for self-hosted mail: rich signals and scriptable rules, built for server operators. It filters at the server, not in your Mac's inbox.For a lightweight self-hosted layer, see Klar for servers.
- Mailinblack
- A French email security service for organizations. It filters mail at the gateway, runs fake phishing attacks to train staff, and gives admins a console. Aimed at companies, not individuals reading mail in Apple Mail.
- Leave Me Alone
- Built for bulk unsubscribing: it follows unsubscribe links for you and rolls newsletters into digests. Its spam blocker learns in its cloud and targets cold outreach. Pick it to prune subscriptions, not as a spam filter.
- Clean Email
- The pick for digging out an overflowing mailbox: smart folders act on thousands of messages at once, rules keep it tidy, and it reads headers only. Filtering means rules you define yourself, so pick it for cleanup, not detection.
- MailWasher
- A veteran Windows tool with a distinct approach: inspect mail on the server and delete junk before it reaches your machine, with Bayesian learning and blocklists. On a Windows PC with POP or IMAP it earns its keep. There is no Mac version.
- Klar
- Pick Klar if you read mail in Apple Mail and want a modern multilingual model that runs entirely on your Mac. No account, no cloud, nothing to hand over.
Full comparisons
Klar next to each one, in detail:
The on-device option
Free, private, in Apple Mail.