SpamBayes Outlook Plugin

NOTE: This is very very early code. If you are looking at this, you have probably been told about it against our better judgement <wink>. Stuff doesnt work correctly. If you want something known to work well today for alot of people, this is not for you. That said, this plug-in works amazingly well! So welcome aboard.

This spam filter uses Bayesian analysis to filter spam. Unlike other spam detection systems, Bayesian systems actually "learn" about what you consider spam, and continually adapt as both your regular email and spam patterns change. The source code is maintained at SourceForge.

Here you can find information on:

Training
Viewing the Spam Score field

Training

Due to the nature of the system, it must be trained before it can be effective. Although the system does learn over time, when first installed it has no knowledge of either spam or good email.

Initial Training

When first installed, it is recommended you perform the following steps:

Create two folders - one for "Spam", and one for "Possible Spam"
Go through your Inbox and Deleted Items, and move as much spam as you can find to the "Spam" folder. Try and get as much Spam out of your inbox as possible.
Select the Training dialog. Nominate your Spam folder for spam, and your Inbox for good messages, and start training.

To see how effective your Inbox cleanup was, you may like to try:

Go to the Filter Now dialog.
Select your Inbox as the folder to filter.
Select Score messages, but dont perform filter action.
Clear both checkboxes so all messages will be scored.
Start the score operation.

You can then look at and sort by the Spam field in your Inbox - this is likely to find hidden spam that you missed from your inbox cleanup.

Incremental Training

When you drag a message to your Spam folder, it will be automatically trained as spam. Thus, as the classifier misses spam (or is unsure about them), it learns as you correct it.
If messages are dropped back into the Inbox, they are trained as good - thus, the system learns what good messages look like should it incorrectly classify it as spam or possible spam.
You will also notice a "Delete as Spam" button (in all folders except the Spam folder) and a "Recover from Spam" button in the Spam and Unsure folders. These buttons have the same effect as the drags above. (Note that currently the "Recover from Spam" option will move the item to the Inbox - this is a bug - it should restore the message to the folder it was originally filtered from in the first place)

Viewing the Spam Score Field

A custom property named Spam is added to all Outlook messages scored. This is a percentage indicating the likelihood of the message being spam (ie, 0% is "certain" ham; 100% if "certain" spam). You can teach Outlook to display this field as a column in any table view, like the standard Messages view.

This takes some work, and has to be done again for every folder in which you want to display a Spam column:

While looking at an Outlook table view (like Messages), right-click on the line with column headers (From, Subject, To, Received, ...). In the context menu that pops up, click on Field Chooser. A box with title Field Chooser pops up.
In the drop-down list at the top of the Field Chooser window, select User Defined Fields
Below the drop-down, you should see a rectangular button with a Spam label . This should be automatically created for all folders managed by the system, but if it does not appear, you will need to add it yourself. To do this, perform the following steps

In the lower left corner of the Field Chooser box, click New.... A box with title New Field pops up.
In the Name: box, type Spam.
In the Type: dropdown list, select Percent. This is the third choice in the dropdown list. Do not select any other format -- it won't work.
The Format: select the first entry in the list - "Rounded"
Click OK in the New Field box. Now you're back in the Field Chooser box, with a new Spam button shown.

Use your mouse to drag the Spam button to the column header position where you want to see the Spam column. You don't have to be precise here -- you can rearrange or resize the column later just by dragging it around.
You're done! Close the Field Chooser box.

Outlook's standard Automatic Formatting features can also be taught how to access the value of this field; for example, you could tell Outlook to display rows with suspected spam messages in green italic. However, for whatever reason, the Outlook Rules Wizard does not allow creating rules based on user-defined fields. That's why this addin supplies its own filtering rules.

Contributions to this documentation are welcome!