Before starting, make sure that you have a folder that will serve as the destination for suspected spam. Create a new one by opening the File menu, selecting New, and then Folder.
  1. Open the Tools menu and select Message Filters.
  2. Select your account from the Filters for drop-down menu.
  3. Click New.

    Thunderbird Spam 1

  4. Give the filter a name, e.g., “SpamAssassin Filter.”
  5. Make sure that Match any of the following is selected.
  6. Select Subject and change it to Customize.

    Thunderbird Spam 2

  7. You will then be able to create a New message header.
  8. Enter X-Score-High (no colon at the end) and click Add.

    Thunderbird Spam 3

  9. Click OK.
  10. Click on the drop-don menu that previously displayed Subject again to select X-Score-High.

    Thunderbird Spam 4

  11. Switch from contains to is.
  12. Enter YES in the text box.

    Thunderbird Spam 5

  13. Under Perform this action or Perform these actions, leave the action as Move message to, and use the other drop-down menu to choose your destination for suspected spam.
  14. Click OK and OK again.