I stopped using Firefox when IE8 came out -- Suffered the same fate as lots of other products -- "Too much Feature-itus". Same with Nero (although Nero has finally gone back to its roots and released a "Nero-Lite" -- probably too late as who uses physical CD's and DVD's any more --certainly a diminishing number of people and now Windows 8 (and even Windows 2012 Server) can mount native iso files from the OS the number will diminish even more quickly.
For email clients on windows Outlook really is the only sensible choice -- office 2007 can still be found very cheaply --outlook hasn't changed much over the years and is still fit for purpose --especially as more people use smart phones and tablets for email rather than computers too. Kingsoft office (Free phone app) works fine too. https://play.google.com/store/apps/details?id=cn.wps.moffice_eng&hl=en
For Non windows systems there's plenty of decent browsers, office suites and email apps around -- Firefox has IMO definitely passed it's sell by date (as has Thunderbird or "Blunderbird" as it seems to have morphed into).