First, thanks for your reply :)
Second, LifeWithQmail was a lot more difficult to follow. Tried it, and it went wrong ...
So here are my run scripts :
cat /service/qmail-send/log/run
#!/bin/sh
VQ="/var/qmail"
exec env - PATH="$VQ/bin:/usr/local/bin:/usr/bin:/bin" \
setuidgid qmaill...