I got to agree about the lack of "bounce" - I could never move my work email to gmail for that reason alone (not to mention my preference of writing emails in my native editor).
Sorry, "bounce" is the command for "Resend mail" (not rejecting email) in a lot of unix mailers. Say A sends an email to B who sends it to C.
If B forwards it to C, the email appears to come from B.
If B "bounces" it to C, the email appears to come from A.
(it's the Resent-to header in RFC 822 IIRC)
So say you get a bug report from A than you know only C can fix, by bouncing it to them they get to easily reply directly to A and get on with it, leaving you out of it...
I use emacs_chrome with Google Chrome which allows me to write E-Mail in Emacs (or actually, any editor). Under Firefox you can use the It's All Text! extension to shell out to any editor.
For Mac users who might not know, the standard text widgets in OS X use a subset of Emacs keybindings, so you can use C-a, C-e, etc to quickly navigate, which is handy if you have your Caps Lock key remapped to Ctrl (in the Keyboard system preferences) and are used to Emacs.
Two caveats: 1) no meta key, which makes navigation less handy sometimes; 2) C-k will kill the line, but I haven't found a kill-ring and you can't use C-y to yank the line back! This has bitten me a couple of times.
It's definitely nothing close to having a full text editing Emacs widget, but I've found it handy.