SpamSieve

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.