Comment 1 for bug 220403

As far as I know, Thunderbird has never displayed an icon in the notification area. Also the system beep is some thing that has annoyed me for a long time. It's not new. Any chance that you had another program installed that you forgot about? Like mail-notification or cgmail?

In the preference menu, under the general tab there are two check boxes: "Show an alert" and "Play a sound" If you check the first you will receive a pop up with each new mail. The second by default will play the system beep, but it is configurable. You can select a different sound to play.