I already tried putting Thunderbird as a shortcut into the C:\Users\<myAccountName>\AppData\Roaming\Microsoft\Windows\SendTo (aka. shell:SendTo) folder. But when I use the "Sent to" menu and select Thunderbird, the file to be attached just gets openned by Windows as if I had double-clicked on it. Thunderbird does not even open a new message. I also tried changing the call of the Thunderbird shortcut in the SendTo folder to: "C:\Program Files\Mozilla Thunderbird\thunderbird.exe" -compose attachment= At least, then Thunderbird opens a new message. But it just writes the path\filename of the file to attach into the attachment section. When I then try to send the message, Thunderbird says it cannot access it under this path. How are you doing this? Thanks!