SpamSieve
bayesian spam filter that bolts onto the mail app you already use
This version
It runs on your Mac and filters mail your Mac has fetched, which means nothing happens while the machine is asleep and nothing is filtered on iPhone unless you set up a training mailbox workflow. It is a plug-in for a mail client, not a mail client: you keep using Apple Mail, Outlook, Postbox, MailMate or Thunderbird and SpamSieve tells it what to move. Major versions are paid upgrades, though the cadence has been unusually slow — 1.0 in 2002, 2.0 in 2005, 3.0 in 2023 — and the version 3 upgrade was roughly half price, or free for recent buyers of 2.x.
Cost over five years
$40 once = 7 months of SaneBox. Over five years that is $325 rented against $39.99 owned — $285 kept, and you still have the app.
SaneBox priced at $65 a year — Snack plan, one mailbox, $5.42 a month paid annually. Checked 2026-09-22.
SpamSieve is not a mail client. It sits beside Apple Mail, Outlook, Thunderbird, MailMate or Postbox, reads each incoming message, and tells your client what is junk. You train it by correcting it, and after a few hundred corrections it is clearly better than the filter built into the client. Michael Tsai has been shipping it since 2002, which on a site about software you keep is the number that matters most.
It earns its place when server-side filtering is not available or not good enough: a personal domain on a small host, an IMAP account whose provider does nothing useful, a mailbox where a false positive would cost you a client rather than a newsletter.
The licence boundary is a major version. $39.99 buys the current one. There have been three in twenty-three years, and the move to version 3 cost existing owners $19.99, or nothing at all if they had bought 2.x earlier that year. As paid-upgrade cadences go, that is close to painless.
Skip it if your mail is on Gmail. Google already filters aggressively and you would be paying to duplicate it. Skip it too if you read most of your mail on an iPhone: SpamSieve only works while your Mac is awake, so the phone gets the raw firehose until the Mac catches up.
What it looks like
What it does
- One-time purchase, stated by the developer as not a subscription
- Works with Apple Mail, Outlook, Thunderbird, MailMate and Postbox
- Learns from your corrections, so accuracy improves with use
- Whitelist and blocklist rules plus notification control for false positives
- Continuously developed by the same developer since 2002
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$49.99The facts
- Price
- $39.99
- Licence
- Own this version forever
- What you get
- One payment buys this major version outright. The next major version is a separate purchase, if you want it.
- Details
- $39.99 one-time for a single licence, $63.98 for the "Family or 2 Users" licence. C-Command describes its products as one-time purchases and not subscriptions. Upgrade pricing exists: when SpamSieve 3 shipped in September 2023 it was $19.99 for previous owners, and free for anyone who had bought 2.x on or after 1 January 2023. Fully featured 30-day trial.
- Free trial
- Yes
- On Setapp
- No
- Minimum macOS
- not stated
- Developer
- C-Command Software (Michael Tsai)
- Price checked
- 2026-09-22
Check it yourself - Price band
- $30 to $60