Mozilla Thunderbird Spam Filtering

Overview

  1. Train Thunderbird on what is Spam (junk mail) and what is Ham (good email)
  2. Let Thunderbird do the Sorting
  3. Continue to Train Thunderbird

Training Thunderbird

In your Inbox collect as large a sample of Spam as is practical. The larger the sample the more accurately it will work.

Mail that Thunderbird already believes to be Spam is marked with a garbage can.
Go through your mail to make sure that legitimate email is not marked as Spam.
If legitimate mail is marked as Spam select the Not Junk button on the toolbar.
If Spam is marked as legitimate email, click the Junk button on the toolbar. After you have sorted your mail, use the client for four or five days to see if Mozilla is accurately catagorizing Spam. This might require some initial work but the time invested is worth it. Once you are satisfied that Thunderbird is able to do a reasonable job at identifying Spam, please proceed to the next step.

Letting Thunderbird do the Sorting

From the top toolbar click the Tools button and from the drop down menu select Junk Mail Controls.

Click on the Adaptive Filter button and check the Enable adaptive junk mail detection

Click the Settings tab.

Click the Do not mark messages as junk mail if the sender is in my address book:
Next click the Move incoming messages determined to be junk mail to: and either select the default which is the Junk folder, or select where you want your junk mail to be kept by clicking on the Other tab.
Lastly check the When I manually mark messages as Junk: Click the Move them to "Junk" folder.

Continuing to Train Thunderbird

No automatic process can substitute for personal judgment on whether any given message is spam or not. Inevitably, even carefully designed filters will have "false positives" (messages that the filter thinks look like spam, but aren't), and "false negatives" (messages that the filter thinks do not look like spam, but are). For this reason, the method given here doesn't throw away suspicious mail without giving you a chance to read it but, rather, diverts it to a mailbox separate from your normal Inbox called 'Junk'. The idea is that you examine this mailbox at lower priority, with the expectation that the messages in it are almost certainly all junk. False negatives will show up in your regular in basket. You can deal with this by periodically "re-training" Thunderbird. Periodically check your "Junk" folder, and if legitimate email is in there click the Not Junk button on the toolbar. Conversely if spam is showing up in your Inbox select it and click the Junk button.