You would need to know what application you plan to use under VectorLinux, e.g.: Thunderbird, KMail, Sylpheed, SeaMonkey Mail, Opera, whatever. Once you decide what application you like then I would just do a Google search such as: " Thunderbird import "Lotus Notes"". That should lead you in the right direction. Each of the Linux apps also have online forums where your question will be answered rapidly, or more likely, the question has already been answered - just do a search on that particular forum; e.g.
http://forums.mozillazine.org/viewforum.php?f=39 .