K9 Spam Filter

K9 Spam Filter

K9 is an email filtering application that works in conjunction with your regular POP3 email program and automatically classifies incoming emails as spam (junk email) or non-spam without the need for maintaining dozens of rules or constant updates to be downloaded. It uses intelligent statistical analysis that can result in extremely high accuracy over time.

K9 learns from its mistakes and becomes better and better at being able to identify spam. More importantly it learns to recognize what you consider to be spam.

K9 is for standard POP3 email accounts only. It does not directly support Hotmail, AOL or any other kind of webmail type systems, nor does it support SSL or secure authentication as used by MSN.
Rating: Very Good
Registration: not required
OS Support: Windows
Installer: Option
Portable: Yes

K9 1.28 - Spam Filter

The Bottom Line
K9 is a wonderfully precise, easy to use and fast learning Bayesian spam filtering tool. It's a pity this gem only works with POP accounts and lacks remote administration.
Pros

* K9 spots spam precisely, no false positives
* User friendly interface
* K9 works with any email client

Cons

* K9 configuration could be easier, better organized
* No remote administration, Web interface
* K9 supports POP accounts only

Description

* K9 checks POP accounts for spam either as a standalone app or as a POP proxy.
* K9 uses advanced Bayesian statistical analysis to detect spam.
* Detected spam can be marked in the subject, or K9 adds a custom X-header for further filtering.
* False classifications can be corrected easily, and K9 learns with each correction.
* In addition to statistical filtering, K9 can use flexible custom-built keyword filters.
* K9 keeps detailed statistics about classifications, and emails can be broken down to the word level.
* Detecting (anti-)junk words hidden in HTML, K9 offers some protection against spammers' tricking.
* Optionally, K9 can query one DNS blackhole list for additional spam checking.
* K9 supports Windows 9x/ME/NT/2000/3/XP.

Guide Review - K9 1.28 - Spam Filter
Finally an application with a short and sweet name. But its name is not the only good thing about K9, and by far not the best.

The best thing about K9 is its ability to detect spam almost flawlessly using Bayesian statistics. All it takes is a bit of training in the easy to use interface (the exception being the configuration tab, which is a bit confusing), and you can filter all spam to a special folder automatically.

While K9 can query a DNS blackhole list server for known spammers, I don't recommend turning this feature on. It will add nothing to K9's junk mail detection accuracy but some to the time it takes to classify mail.

Working as a POP proxy, K9 can be used with just about any email client. Unfortunately, this also means K9 is restricted to POP accounts. IMAP users must look elsewhere for advanced spam protection.

In addition to IMAP support, remote administration (maybe via a Web interface) would make a nice enhancement for K9.