newbie postfix problem

[Joolz]

Hello everyone,

I have a problem with postfix on a standalone fedora box. In order to
be able to mail with the outside world, I put this in main.cf:

myorigin = myprovider.com

This works, but the problem is that mail sent to an address without
the domain part, is sent to myprovider.com. This is most of the time
not what I want, e.g. mails about logwatch (which are by default sent
to "root") etc. should _not_ go to root at myprovider.com, but to
root at localhost.localdomain.

What do I have to do to be able to mail with the outiside world, and
at the same time have localhost.localdomain as the default domain?

Thanks!

-- 
Fedora Core release 1 (Yarrow) Linux 2.4.22-1.2129.nptl 11:27-11:31