multiple smtp

Tech-Archive recommends: Fix windows errors by optimizing your registry

im running my business from home.
I have a small peer to peer network with 5 pc's and thought it was wise to
change it to client/server network
im using many different domains for email and many different addresses per
domain (private/business etc)

i installed SBS 2003 and the first thing i wanted is my email working as i
had (pop).
Exchange is working and i can send and receive email from the default
account.
i added a 2nd domain without problem, but...

everyhthing is received by the default email address
im not able to reply with a different email address
i found some trics to set outlook client to be able to select different
email to send from, but even when email is send to abc@xxxxxxx, its
converted to the default address like default@xxxxxxx and this address is
used when replying ...
Also in OWA only default address is available

how can i configure exchange so that i can receive email without the
emailadress is converted to the default address.
And that i can choose the emailaddress to send from (use multiple
addresses)And this all also available in OWA

Any ideas?

Thanks,
otto
.