Hi,
Here are some step.
1/ have your domains registred with the same IP
  eg. domain.com @ 111.22.33.44
        domain1.com @ 111.22.33.44
        domain2.com @ 111.22.33.44
 I use dynnds.org to register domain and free domain - I have 3 free doamion and 3 register doains all with the same ip.
2/ On you sme server create two new ibays with htlm option enable
   Public access via web or anonymous ftp     = Entire Internet (no password required)
   Execution of dynamic content (CGI, PHP, SSI) = ENabled    
   Move deleted files to Recycle Bin  = Enabled     
and of course you have the primary ibay.
3/ Add the new doamin to the SME server via the domains panel and point each domain to the appropriate ibay.
 eg  domain.com => primary Ibay
      domain1.com => ibay1  (virtual domain)
      domian2.com => ibay2  (virtual domain)
you can now setup indvidual web site for each doamin under the html directory of the ibays.
You will also be able to receive email under each of the domains. Andy uers that you have setup on your sme server can receive email under any of the domain names setup on your server.
check out these two doains 
www.gregalmeida.homeip.net, 
www.icewtr.homeip.net  or 
www.icednetworks.com (under construction) all of these three domain are under the one server and IP address, and i can receive email on eny of them.
If you need more detailed how-to let me know and I will do one and post it on my web site.
Hope this helps.
Good luck.
George 
 
  email: george@icednetworks.com