Opening Thunderbird (I've been using it for years) I get "Alert: Sending of password did not succeed. Mail server pop.windstream.net responded: [IN-USE] account is locked by another session or for maintenance, try again. After clicking OK: "Login to to server pop.windstream.net failed live.mozillamessaging.com uses an invalid security certificate. The certificate is not trusted because no issuer chain was provided.(Error code: sec_error_unknown_issuer)