This started about ten days ago. I use Thunderbird on a Windows 20 desktop. I have three email accounts set up. Every few minutes the chime alerting to new mail bings on the least-used account and a little red bubble appears on the Thunderbird icon in the tray with the number of new emails -- sometime is says 2 0r 3, sometimes 30 or 40. But, none of the folders in this account have any new email. As soon as I click on the account header (which has turned blue to show new email) the number bubble disappears from the Thunderbird icon and the account header turns back to black. Then, a very few minutes later, the chime goes off again. I am stumped. Has anyone else experienced this?