Notice: The plugin has been updated since this posting.

The latest release of the WordPress SpamAssassin Plugin includes the #1 most requested feature (and in fact, so far the only requested feature). Is it actually working?

I’m pleased to announce version 0.4 of the WordPress SpamAssassin Plugin. This plugin filters all of your blog comments through SpamAssassin, recognized as the Internet’s best spam killer. It is so good at sorting spam from non-spam that adapting it to blogs seemed like a natural thing to do, especially since I ran into trouble with every other solution out there.

New in this release: The plugin now writes logging data to the server error log whenever a comment is screened. (You may need to request the error logs from your web host.) An example log entry looks like this. This represents a legitimate comment. A log entry for spam looks similar, but shows Spam: True. Thanks to thoellri for the idea.

[client 207.177.45.61] PHP Notice: SpamAssassin: screened comment from 207.177.45.61 by IO ERROR at error%40ioerror.us. Spam: False -2.8 / 5.0 in /var/www/example.com/htdocs/wp-content/plugins/wp-spamassassin.php on line 105, referer: http://www.example.com/2005/01/16/alive-and-kicking/

To use the SpamAssassin plugin, you will need a SpamAssassin server. Many web hosts already have one for their incoming email; ask them for the address and edit the wp-spamassassin.php file to include it. If you are self-hosted, you will need to install SpamAssassin on your computer, if it isn’t already installed.

You can also customize the threshold at which suspicious messages are sent to the moderation queue. Suspicious messages are those that SpamAssassin thinks might be spam, but isn’t entirely certain. Messages identified as definitely spam are discarded. To use this feature, copy the tag in wp-spamassassin.php into your spam keywords list. (I don’t do this automatically in order to avoid corrupting your list or introducing blank lines.)

Update 22 Jan: I have updated the plugin to version 0.5. This new version fixes a problem with false positives on WordPress 1.2, and works around a common PHP server misconfiguration which causes some users to receive “Headers already sent” messages. View or download it from the new permanent page.