From MozillaZine Knowledge Base
Problems some people have experienced with Thunderbird's Junk Mail Controls:
- Thunderbird marks messages as Junk as expected, but it stops moving messages to the Junk folder. Sometimes it starts moving messages again; sometimes some messages are moved but others are not.
- Manually running junk filters ("Tools -> Run Junk Mail Controls on Folder") works as expected, including moving all messages marked as Junk to the Junk folder.
- The Junk Mail Log ("Tools -> Junk Mail Controls -> Junk Mail Log") may erroneously say the messages have been marked as Junk and moved. (needs to be verified)
- Manually marking a message as Junk (clicking in the Junk column in the mail list) does not move the message to the junk folder.
As of 17 November 2004 this problem is a known bug in Thunderbird 0.9 and possibly earlier versions. These solutions have been proposed, but none are verified to always work:
- Workaround: manually run the junk-mail filter: "Tools -> Run Junk Mail Controls on Folder".
- Delete all messages in the Junk folder.
- Turn off junk mail logging. Go to: "Tools -> Junk Mail Controls...", click the "Junk Mail Log" button, uncheck the "Enable the Junk Mail Log" checkbox. Try to flag an e-mail as Junk and see if it works. [Note: you can re-enable the logging after this.]
- Not for users with limited computer skills: close Thunderbird, find your profile folder and delete the "Junk.msf" file. WARNING: Deleting the wrong file can cause loss of your e-mail.
- Not for users with limited computer skills: close Thunderbird, find your profile folder and delete the "Junk" file and "Junk.msf" file. Create a new, empty "Junk" file. WARNING: All messages in the Junk folder will be irrevocably lost. Deleting the wrong file can cause loss of other messages. (To be on the safe side, just rename "Junk" and "Junk.msf" to "OldJunk" and "OldJunk.msf".)
- Not for users with limited computer skills: I found the problem in the account folder: there was not the "Junk" file and there was a folder named Junk. I've deleted the folder Junk and i've created a file named Junk and the problem was solved. Hope is helpful.
- If you created any filters that mark target messages as junk: Be sure to include the additonal action of "Move Message to" "Junk on <account>". (During the download process, Junk Controls will only move messages to Junk that *it* - Junk Controls - marks as junk.)"
- Manually marking a message as junk does not work make sure to make sure to enable Tools/Options/Security/Junk/ "When I mark messages as junk: Move them to the account's "Junk" folder