I use four SMTP email accounts extensively, and all have mail flowing in constantly. Now that I've installed Thunderbird in my Mandrake setup, though, only two of the accounts are downloading mail. All the accounts are set to "keep messages on server", and I can retrieve them from other mail clients, but not Thunderbird. For some reason, it thinks that the messages are not new and doesn't downloading them.

Does anyone have any clue what's happening here? Like I said, other clients work just fine when set up with the exact same parameters.