To see the filter log in Thunderbird * Tools > Message Filters * click on 'Filter log' button If it has been enabled, it will show filter log info. The 'filterlog.html' file is in your profile folders. How to locate it: In Thunderbird * Help > Troubleshooting Information * Under 'Application Basics' section - half way - Profile Folders - click on 'Open Folder' A new window opens showing the contents of your 'profile name' folder '''If looking for a filter log in a pop account:''' * Click on 'Mail' folder to see contents * Click on 'pop mail account name ' folder '''If looking for a filter log in an imap account:''' * Click on 'ImapMail' folder to see contents * Click on 'imap mail account name ' folder You should see the 'filterlog.html file You can open it using a simple text editor program like Notepad. Then use 'Edit' > 'Find' to search.