How do I create a POp3 address for different Domains

I'm running Exchange server 2000 on windows 2000 advanced server. So far, i have followed the steps on the help documents that i found on the internet and the instllation CD, i followed every step on the CD and i have successfully installed MS exchange server with active directory and DNS.

I have 3 domains running on my domain controller. I want to create, seperate POP3 adresses for each of the domains.

For example, i have www.abc.com, www.xyz.com and www.pqr.com. i want to give them separate mail accounts and
they need to be able to deal with their mail on their separate pop3 accounts.

I am able to send and receive mail on email account assigned to the administrator account in the active directory. in outlook from outside, if i use the IP adress instead of the POP3 and SMTP adress, then i am able to easily send and receive mail.

I think that my problems would be solved if i manage to create POP3 and SMTP adresses. or Do i have to do something else?

Has anyone got any ideas, or does anyone know a step-by-step page on the net, which they could show me.