just letting people know what i've finally chosen - i use gmail by default even though i also use maxthon as my main browser, which has a problem attaching multiple files to google mail.
after trying the suggestions in this thread: http://www.donationc...ex.php?topic=17927.0
i've added "Affixa" (the free version) http://www.affixa.com/
to my system. this gets around the maxthon browser problem of not being able to select multiple files when uploading to an email (you have to upload each file individually regardless of the google mail "advanced" settings of allowing multi upload). Affixa lets you attach/upload several files in one go. great.
Affixa also makes gmail your systems default mail client - so clicking on any mailto: link will open a new gmail "compose" window in your browser with the correct "to" address completed. (i'm not using firefox as my main browser so i'm not interested in any related solutions there - nor with chrome.)
Affixa main window for attaching several documents at once (drag and drop didn't work but copy and paste does).
then, finally, i use "Digsby" http://www.digsby.com/
which has the best system tray email notifications i've seen. just by clicking on the system tray icon you can do several actions - all without even opening up gmail in your browser.
open, mark as read, archive, delete, report spam - just by accessing the drop down menu from the tray icon. and it lets you quickly perform these actions on several emails at once. it's so easy (and quick) it makes opening your inbox feel very tiresome.
you can, of course, click to go to directly your gmail inbox or click a link to compose a new email.
as an added bonus you can have more than one gmail account monitored too - or yahoo, or hotmail, etc. i also use digsby for all my chat clients (though it's still lacking a proper "Skype" feature).
menu accessed via try icon (circled in red) note the quick links and useful info displayed for each email.
popup message indicating you have new mail (i tend to ignore this feature and just click to view the list of new emails shown above).
i just thought i'd mention all this as i know there are a lot of people trying to make gmail their system default for emailing - without using a standalone mail client program (e.g. outlook or thunderbird). it might not be the ultimate solution having two programs doing the work of one (or three programs when you include your browser), but for the features and ease of use this setup provides i'm more than happy.
i'm surprised Digsby can't do the work of Affixa and respond to mailto links as it does everything else (maybe that will come eventually).
(edited: to add small screengrabs).