Exchange server on linux?

[Darren Cook <darrenj@example.com>]

Is anybody using TradeServer in an office environment (i.e. with
win98/Outlook machines):
  http://www.bynari.net/Products/products.html

I'm especially interested in if calendar sharing works, and if there are
any issues with Japanese clients (English user interface to the server
itself is no problem).

I'm also interested in any similar products (I know about HP's OpenMail:
http://www.openmail.com).

Darren