If you install an email server program such as Weasel from Peter Moylan, you can setup it up so email that comes in for one user is automatically copied to several other users [by extension, to, or from several users]. ie, its all to do with creating one or more alias's which still have seperate mailbox's.
You can then have each computer have its own user (mine1@, mine2@) which are all receive alias's for your primary email address(s). As each computer access's that account, then it deletes email after retrieve from that computers POP email account. This allows each computer to retrieve all the email sent to that one user with no double ups across different computers. When any of the computers send email out, they can do so via Weasel or via your external SMTP server using the email address(s) that you wish the outside world to reply to.
Hope that makes sense. Probably best described with a piece of paper and a pen to make a flow chart
