Try this. Download this addon: * https://freeshell.de//~kaosmos/mboximport-en.html Make sure Norton Live update is up to date. Create a new folder on the desktop. in Thunderbird, right click on folder and select: ImportExporttools > Export all messages in the folder > EML format Where to save - choose the folder you just created. Now you will have each email as separate files. Then run Norton scan on the new folder containing the emails as individual .eml files. It will scan and locate which email has the virus. Then you will know which email has the problem and you can delete the offending email and empty the trash and Junk folders. then compact all your folders including the Deleted and Junk folders.