Multiple SMTP domains on one exchange server

Hi all,

I am currently trying to set up our exchange 2003 server to host email for about 8-9 domains. Our setup is that we have one domain controller(w2k3), which hosts all users for 4 different in-house companies. Basically what I need to set up exchange to handle all the seperate smtp domains. Is it possible to use exchange to set all the users working for abc.com, to adopt the email address @abc.com, and etc etc for def.com, ghi.com…..
Also, we are currently using pop3 accounts and pst files but we would like to migrate to using server mailboxes, is there an easy way to do this