Mail Widget Search

I have tried every single mail checking widget on this site. I am looking for a mail checker widget that acts identical to my email client (Thunderbird) in identifying only new mail that I have not yet downloaded. If my email client, as well as most other clients, do not redownload mail that I have intentionally left on the server, then there must be a mail checker widget somewhere that will tell me only the mail that has not already been downloaded. I'm looking for a clean, configurable, widget that allows me to set up a single POP3 account and dictate how often I want it to check for new messages. Does anyone know of a solution? Thanks....