Thunderbird keep retrieving all yahoo emails from pop server

Question

Thunderbird suddenly retrieves all my 2000+ emails from yahoo pop server every time I check mail. My account setting is to have the mails stored in the server until I delete them.

Answer 1

You may need to delete the popstate.dat and let Thunderbird recreate it (that's the file that keeps track of which messages have been downloaded). See this for details. It will have to download all the messages one more time, and then it should be able to keep track.