More info needed
You don't specify which version of KMail.
Assuming that it's the same version that I use, then it's fairly easy, but not terribly sophisticated. All that it is, is a list of potential addresses. I.e., it's a list of lines of text which, if selected, will be entered verbatim into the To: field. I believe that I started this from the menu-bar (though that may have been several versions back). There may also be a button next to the To: address that you can click on which displays recently used addresses (not quite the same as an address book, but the exact same contents as will be put into one when you create it).
I haven't tried, but it seems plausible that one could enter an address such as:
and have it parsed correctly. (Unfortunately, I'm at a Win95 machine at the moment, so I can't test this right now, or examine the details of using the address book).
OTOH: I seem to recall that the recent system came with a KDE application that kept a more full-featured address book. Sorry, I don't remember it's name. I haven't gotten around to using it much.