From MozillaZine Knowledge Base

This article was written for Thunderbird but also applies to Mozilla Suite / SeaMonkey (though some menu sequences may differ).

Thunderbird displays a new mail icon in the system tray even if you uncheck all of the checkboxs in Tools -> Options -> General -> "When a new message arrives". Supposedly you can disable that icon by setting the update.showSlidingNotification and mail.server.default.notify.on preferences to false using Tools -> Options -> Advanced -> General -> Config Editor. However, that doesn't seem to work with Thunderbird 1.5.

Windows XP or later

A workaround is to configure Windows to hide the icon for you. The system tray doesn't have to show the icon when you do this.

• Right click on the Start button and select properties.
• Select the Taskbar tab.
• Check "Hide inactive icons" (if its not checked) in order to enable the Customize button.
• Press the Customize button.
• Find the envelope icon in the list and select it. In the dropdown that appears, select "Always Hide".
• You may find that checking "Hide inactive icons" set the other icons in the list to "Hide when inactive". Select each of them and set them to "Always show" if this occurs.
• Press the OK button.

Earlier versions of Windows

Use a utility program such as TraySaver to hide the icon for an application in the system tray.

Linux

You need may to install the Mozilla New Mail Icon (Biff) extension to display an icon in the standard (FreeDesktop.org) system tray (used by GNOME, KDE and IceWM) when new mail arrives. Uninstall it if you don't want this functionality. There is a seven year old bug report requesting new mail notification in the system tray.

Ubuntu installs Thunderbird without that extension, and displays an icon in the system tray when new mail arrives. It installs a Alltray program thats designed to "dock any application with no native tray icon (like Evolution, Thunderbird, Terminals) into the system tray.". They also have builds for SuSE, Fedora, Debian , Gentoo and "generic". Try searching for tray and/or Thunderbird in your distributions package manager to see if you have a similar package.

See also

• Modify Thunderbird settings
• Minimize to system tray (Thunderbird)