I haven't tried this, but it should work ...
under /var/qmail/alias create a file (or if it exist, modify it) named
.qmail-everyone
in it place a & and your email address ie ---
&admin
so everytime an email is sent to everyone@yourdomain.xxx it should be sent to admin@yourdomain.xxx ----
you could probalby setup another alias only known to you that would ultimately forward to everyone if you think its worthy..

hope this helps