Multiple mailboxes

[#1]

I'm new to Outlook and am not sure how to set up more than one user in fairly particular circumstances. I'm using Outlook 2010.
I wish to have emails addressed to user.1@mydomain, user.2@mydomain2 and user.3@mydomain3 to fall into separate inboxes and for replies to show they are from user.1@mydomain, user.2@mydomain2 and user.3@mydomain3 as appropriate.
I also need to have emails addressed to user.4@mydomain to be automatically copied on to a friend (on Virgin) at friend@hisdomain with me receiving a copy also.
A simple explanation on how to do the above would be *extremely* welcome!
TIA

[#2]

http://www.plus.net/support/email/newemail.shtml?supporta=addaddress
http://www.plus.net/support/email/setup/index.shtml?supporta=emailsetupguides
Note: the domains need to be hosted by Plusnet to have email accounts.
Note2: Each domain does not have it's own set of email accounts... email1@domain1.com & email1@domain2.com are the same and go into email1@yourname.plus.com and it's the yourname.plus.com mailbox you need to use when setting up your email client but you can still use the domain mailbox as the actual name people see and reply to.

[#3]

You can still have separate mailboxes for user.1@yourname.plus.com ,  user.2@yourname.plus.com ,  and user.3@yourname.plus.com ......  To set them up, see Reply #2 here:-
http://community.plus.net/forum/index.php/topic,96085.msg810196.html#msg810196
Each user would collect from his own mailbox using his own password. And you can set up a redirect so that email addressed to, say, user.3 goes to another address altogether (but I don't think you can copy like this, only redirect).
HTH
Chris

[#4]

Thanks for your help: sorted! Just a pity I can't automatically send an email on to both my own mailbox and a third party's...