Description:
Thunderbird's Desktop Entry (/usr/share/applications/thunderbird.desktop) contains the following Exec line:
Exec=thunderbird

As you see, no argument is being passed to Thunderbird. When invoking Thunderbird from other applications, e. g. in order to write an email to a certain email address, this leads to Thunderbird being opened "as usual", e. g. as if started directly without an argument (which is exactly what happens). What we want to happen is the composer to be opened in order to compose an email to the address that _should_ be passed to Thunderbird as the first argument.

Compare invoking Thunderbird with "thunderbird" to invoking it with "thunderbird mailto:foo@example.com". The latter command opens the composer, the former doesn't.

In my case, this bug prevents me from using Terminator's (a terminal emulator) context menu to compose an email to a selected email address using Thunderbird.

Additional info:
* This affects thunderbird 3.1.10-1.

Steps to reproduce:
* Get Terminator (or some other program using PyGTK's "gtk.show_uri()" method or its GTK+ equivalent in order to open URLs).
* Make sure Thunderbird is installed and set as the default mail client/mailto scheme handler (e. g. by issuing "xdg-mime default thunderbird.desktop x-scheme-handler/mailto". Restart Terminator after doing that!).
* Somehow output an email address in Terminator -- e. g. by issuing "pacman -Si thunderbird".
* Right-click on the email address and select "Send email to...".
* Watch Thunderbird being opened as if having been started directly. No composer window is opened.

Proposed solution:
Change the Exec line in Thunderbird's Desktop Entry to read:
Exec=thunderbird %u

See http://standards.freedesktop.org/desktop-entry-spec/1.0/ar01s06.html .