Statistical Filter Options (Content Filtering)

Use Statistical Filtering to create and maintain the mail domain specific exclude list, specify the action to take when spam is identified, and specify whether to use the primary mail domain's word counts or create new ones.

Statistical Filtering examines each word in an email message and evaluates how often the word appears in spam and non-spam email. The entire message is then evaluated based on all of the word values to determine whether it is likely to be spam.

Use: Set the following options to configure statistical filtering.

No Filtering. Disables statistical filtering.
Current Domain (selected by default). Select this option to define statistical filtering settings specific to the current mail domain.
Primary Domain (default for non-primary domains; not available for primary domains). Select this option to use the primary mail domain's statistical filtering settings instead of creating new settings for the current mail domain.

Note: Selecting Use -> Primary Domain for Non-Primary Domains will utilize only the statistical filter for the Primary Domain. The Exclude List is separate from the statistical filter, and must be set on a per domain basis. The primary Exclude List can not be used for non-primary domains, unless the "exclude-list.txt" is physically copied to the non-primary domain folder.

Exclude the following words from Statistical Analysis:

Word list. Click a word to modify. Click or to sort the list.
Add. Click Add to create a new word to filter for the current domain.
Delete. Select a phrase that you want to delete from the domain, then click Delete to delete the phrase.

Note: Added words can be found in "exclude-list.txt" under the \IMail directory.

Action taken on email determined to be spam:

Action:
- Delete. Immediately deletes the message.
- Forward to Address. Forwards the message to an email address entered in the text box to the right of this option. By default, messages are sent to the root address and stored in a mailbox called "bulk". Example
- Insert X- Header (default). Inserts an X- Header into the message indicating that the message was identified as spam by statistical filtering. For more information, see Spam X-Header Explanations.
- Move to Mailbox. Moves the message to the user's mailbox specified in the text box to the right of this option. If the mailbox does not exist, it is created.
- None. No action is performed on messages identified as spam by the statistical filter.
  Tip: We recommended that you select the Insert X- Header option instead of Delete until you know that the antispam options are setup correctly.
  
  Note: For more spam options see Using Delivery Rules to Filter Spam.
Prefix subject with. If selected, the subject of a message that is identified as spam by the statistical filter will be modified to begin with X-IMail-Spam- Statistical.

These options control the underlying functionality of the statistical filtering feature and are dependant upon each other to effectively identify spam. If you have a significant number of legitimate messages that are being identified as spam (false positives) or vice versa, you may need to adjust these options.

Note: The default settings are appropriate for most systems. We strongly advise that ONLY experienced administrators modify these settings. Setting these options too high or too low could hinder IMail Server's ability to identify spam.