How do the spam filtering options work?

Webmail has several options that can help manage spam (unsolicited commercial email). These options are:

Filter spam to folder
Display Spam score in message view
Show spam score in all folders
Spam filter threshold setting

All of these options are designed to work with RESPITE. RESPITE is RPI's web-based spam filtering system. Think of RESPITE as a way to tell the mail servers that (1) you have a spam problem, (2) how agressivly you would like the spam blocking to be, and (3) what exceptions, or other modifications, should be made to the default filter rules. For more information about RESPITE and spam, see: Spam and Spam Blocking (RESPITE).

How Webmail works with Respite

If you are familiar with RESPITE, you know that it gives email messages a spam-score. The higher the score, the more spam-like the message appears according to RESPITE's rules. Respite can be configured to reject messages that score higher than a given score (e.g., 10) and trap messages with a given, lower, score (e.g., 3). Trapped messages are held, until you log into RESPITE, and either declare them spam, or not-spam.

Viewing spam scores using Webmail

A problem with using RESPITE is that it is not always easy to find the spam score of a delivered email message. Respite displays the scores of trapped and rejected messages, but the score of delivered messages are hidden in email headers, which can be difficult and/or tedious to view with many email clients.

Webmail has two options for displaying RESPITE's spam scores.

Display Spam score in message view

This option will display the spam headers when viewing a message. The display includes: the spam score (and Bayesian estimation if available); the current RESPITE stream (if not equal to the current login); Bayesian voting links; and links to configure RESPITE sender, domain and custom rules.
Show spam score in all folders

This option adds a spam ``score'' column on the folder index pages, allowing viewing and comparison of a larger set of scores.

Sorting on the spam score will quickly reveail the effect of changing the RESPITE trap or reject threshold. For example, if most of the spam RESPITE missed scored above 4, and all of the legitimate email scored below 3 it is safe to set RESPITE to trap at 3 or 4. If a legitimate email scored high, RESPITE custom rules can be used to adjust the spam score down. Or, a rule can be added whitelisting the sender.

Using Webmail as your spam trap

Webmail can also be used as your spam trap. The trap is not as full-featured as the RESPITE trap, but it is good-enough for many uses, and can cut down on the needed trips to RESPITE.

To trap spam in a Webmail folder:

Log into RESPITE and set the "trap" level to to the "reject" level. This is done on the "Options"/"Stream Options" page. the value choosen should be high enough to not catch legitimate email, but low enough to reject obvious spam. A value of between 10 and 15 is a good starting value, with 10 rejecting more messages.
Create a Webmail folder (on the Webmail Folder Manager page) for holding the trapped messages. Lets call this folder "spam".
On the Options/Account Info page select the "spam" folder in the "Filter spam to folder" select list, and check the corresponding checkbox.
Set a spam threshold for trapping messages. This should be lower than the trap+reject level set in RESPITE, but high enough to catch likely spam. A value between 3 and 5 is typical, with 3 trapping more messages.
If desired, check the ``Display Spam score in message view'' and ``Show spam score in all folders'' options.
Click the "Save" button.

Once configured, email that contains a RESPITE spam score header, with a spam score that exceeds the trap threshold, will be filtered to the designated spam folder. You can review the trapped messaages by visiting the folder. The messages can be viewed, moved, deleted, and so on, like any other message.

Using Webmail for Bayesian training

If you have Bayesian training enabled in RESPITE (see the RESPITE documentation), Webmail can be used to train messages as spam or not-spam. First, the "score" column will contain active links which train messages as spam. This column can be viewed with the "Show spam score in all folders" option, and is always displayed in the designated "spam" folder.

Second, Webmail will create Bayesian training links---even if RESPITE has not been told to add training links. These links are displayed if the "Display Spam core in message view" option is enabled. Webmail constructs the links from the email message headers without altering the body of the email.

For Bayesian traning links to work you must first be logged into Respite in a different window. A future release of Webmail+RESPITE will not require the separate logins.

Don't forget to configure a Bayesian filter rule in Respite. This is done on the Rules/Bayes settings page. A rule adding 5 points to messages scoring 95% or higher is usually sufficient. The RESPITE documentation contains a more detailed example.

For more information see: Spam and Spam Blocking (RESPITE).

Last modified: June 7, 2006