I have several email addresses...............and currently use different ones for different sets of people.
In that case you'll need to setup a new account in WLM for each email address.
After doing that you'll notice that each email account will have its own Inbox and Sent Items folder.
.......ie all replies come to my inbox, and all sent items are in the sent file no matter which email address I use.
You can configure WLM to do that by adding "All inbox" and "All sent items" to the "Quick Views" section of the folder list. It's basically a custom view that displays the sum of all Inbox and Sent Items folders.