Thunderbird hung on same email and duplicated it about 200 times and would not load any new messages after that one. I deleted popstate.dat file and it stopped repeating that same message. Now I can no longer receive email but I can send email. When I try to get email it says that it is getting one of over 9000 messages but then it says no messages to download. My settings are correct and have not changed. I have uninstalled and re-installed Thunderbird many times but I still can't receive email from att.yahoo server. AT&T was no help. Any suggestions? Thanks!