make browser tab active on earlybird click?

[fbu924]

Hello: earlybird 34.0a2,w8.1.2. When clicking on a link in an email, how do I make the link open active in the browser? The link does have a tab in the browser (FF stable 32), but it's not active. I looked in config ed. (earlybird's ) using searchwords "newwindow" and "browser". 2 results appear which may or may not apply: "browser.link.open_newwindow" (default status, value 3), and "browser.link.open_newwindow. restriction" (default, value 0). But I don't know what these values mean & won't mess with them.
- I don't even know how to fix this in FF, if applicable, not knowing how the 2 apps talk to each other. (Yes I do use FF config ed & tabmixplus addon). Further I post here, not in other t-bird forums, cause I've not used a stable t-bird for 5+ yrs. (so I don't know if this is a prob. in stable t-bird). Thank you.