getting control of tabbed browsing

[Claude Jones]

One thing that I can't get a handle on in Firefox is how to force a 
single window, with all URL's clicked on from anywhere always opening a 
new tab in my open window. For instance, if I receive an email and it 
contains a link, clicking on it opens a new window. There are other 
examples of this. I've downloaded two extensions, Tabbrowser Preferences 
and QuickTabPrefToggle, but if the latter installed its toggle I can't 
find it, and the former gives you a few more options in prefs but none 
seem to force single window behavior. What am I missing?

-- 
Claude Jones
Bluemont, VA, USA