It would seem that Microsoft only wish to pursue their own agenda rather than provide customers with that which works and which they want. First they drove out Netscape, and now their own Outlook Express. As I recall Netscape was very similar to Express. Is their no-one capable of writing a program which comes without the annoying add-ons of Windows Live? To me Thunderbird is not the answer.
If you don't want add-ons, use Web based email like Yahoo or Hotmail.
i'm a huge fan of Thunderbird. Version 3.0 is vastly superior to its predecessors. If your going web based... Gmail is the best. Hands Down