[exim] .forward and pipe command 'reboot'

Hello,

i will do the following (is typed in my .forward-file):

> if $header_subject: is "reboot" then
>    save "$home/.imapmail/Trash"
>    pipe "/sbin/sudo reboot"
> endif

You see, i will reboot my server by mail.
The save-command works ok,
but the pipe-command doesn't work.

In sudoers the user who receives the mail has all rights.

Joachim