Hi, solved the problem and thought I'd post it, in case it helps someone else... I couldn't solve the problem on my machine by the other posts I read (e.g., deleting the popstate.dat with TB closed didn't help; also the offending multiply downloading file was no longer visible in my mailserver In Box, so I couldn't delete it there). My mail server is yahoo.de, so the below should be adapted to yours (e.g., yahoo.com or otherwise). I moved ALL In Box mails on my yahoo.de mail browser to another folder I created there (at the yahoo server mail browser, not local on my computer) I did find the offending file that keeps downloading only in the Junkmail folder on yahoo.de and deleted it (you may not find it there; deleting it from there may not matter). I deleted all copies of that file also from the Inbox in TB (you can move a copy of it to another folder to not loose it; mine actually wasn't junk.) I closed TB. I then deleted the popstate file from its folder: Mine was here C:\Users\yourname\AppData\Roaming\Thunderbird\Profiles\t6ahmsju.default\Mail\pop.mail.yahoo.com (you can find yours in TB under the Help pulldown menu, then click troubleshooting information and click the "show folder" button. Then open the Mail folder and then the folder with the name of your mail provider (mine was pop.mail.yahoo.com)). I restarted TB: it worked properly I then returned to yahoo.de, moved all the mails (that wouldn't download before) from the created folder back into the in box on yahoo.de I went back to TB and used get mail to retrieve those, too. Problem solved. It could be that not every step is needed, but they are all easy enough and it worked.