Each mail account would have it's own message filters, but at this point I have no idea whether you simply reinstalled Thunderbird and setup a new IMAP mail account to reconnect to server or whether you manually reinstalled the entire Thunderbird profile folders from a pre made external backup or whether you used the 'windows.old' folder to rescue folders. You should have a ''''windows.old'''' folder created by Windows OS on the C: drive. It is temporary backup. It should contain this location: * C://Users/User Name/Appdata/Roaming/Thunderbird/ I would advise you access the 'windows.old' folder - locate the 'Roaming' folder and get a copy of the 'Thunderbird' folder and put it somewhere eg: external drive as a backup. That 'windows.old' folder will only be available for about a month after which Windows OS will auto delete it. Pop and 'Local Folders' mail accounts are located in the 'Mail' folder: eg: C://Users/User Name/Appdata/Roaming/Thunderbird/Profiles/<profile name>/Mail/<pop mail account> Imap accounts are located in the ImapMail folder: eg: C://Users/User Name/Appdata/Roaming/Thunderbird/Profiles/<profile name>/ImapMail/<imap mail account> In the respective 'mail account' folder this is the name of the file that contains Message Filters: '''msgFilterRules.dat''' That file can be copied and pasted into the correct account name folder of the currently used profile. In Thunderbird you can access current profile: * Help > More TRoubleshooting Information * Under 'Application Basics' - half way - Profile Folder - click on 'Open Folder' - see image below A new window opens showing the contents of your current profile name folder. * Exit Thunderbird now - this is important. * For POP: click on 'Mail' folder * For IMAP: click on 'ImapMail' folder * Click on the mail account folder to see contents. You will see a 'msgFilterRules.dat' file at this point it is likely to be empty because you have no filters set up. * Delete that empty 'msgFilterRules.dat' file or temporarilly put on desktop - you can delete later. * Then paste in the copied 'msgFilterRules.dat' file which you retrieved from the 'windows.old' Thunderbird folder. Repeat the copy paste of 'msgFilterRules.dat' for each account. Note: you should make sure it is being copied from and pasted into the correct account name folder. If you get it wrong - do not panic, you can repeat this process to access the profile and try again. You can open 'msgFilterRules.dat' using rigth click and 'open with' - select Notepad text program to check what filters it contains.