If you have not done so already, run, don't walk, to these URLs:

http://www.kroupware.org (home page)
http://www.kroupware.org/concept-1.0.1/index.html (Architecture Paper)
http://kolab.kde.org/
http://pim.kde.org/development/kroupware.php

Read the first 20 pages of the Architecture Paper and then think about what this means.

Here's what the kroupware site says about itself:

The companies Erfrakon, Intevation and Klar≈lvdalens Datakonsult have been contracted by the German Bundesamt f¸r Sicherheit in der Informationtechnikt (Federal Agency of IT-Security) to provide a Free Software groupware solution accessible with Windows running Outlook and GNU/Linux running KDE clients. These companies do the develop in an open manner as much as possible and maximise the benefits for the Free Software community. Kroupware is the name for the activities done by this group under this contract.

Basically, the German gov't has commissioned a MSFT Exchange replacement called Kolab. It will be written for KDE 3 on Linux (Debian, Red Hat, or SuSE), and it will be open source, under the GPL, and free as in cost. It will use current KDE software for the client, and currently existing technologies for the server. It will be based entirely around open standards. MSFT Outlook 2000 users will be able to connect to it via the Bynari plugin (don't have the exact price, but if I remember right, it's quite reasonable).

Here's what you will be able to do:

Email
Tasks
Calendar
Contacts
Notes
Share resources

Here's the software on the client:

KMail
KOrganizer
KAddressbook
Kitchensync (for Palm sync)

Here's the server software:

Postfix (therefore, maildir format for messages, not mbox)
Cyrus IMAP (therefore, no procmail; instead, Sieve)
Apache
Inet Daemon
ProFTPD
OpenLDAP2

Here are the standards:

LDAP
FTP (for MSFT clients only)
SMTP
IMAP
POP3
MIME
HTTP
HotSync
vCal
vCard
PGP/GPG

Importing from MSFT Outlook format (pst) to the KDE clients will be supported as well.

As of this writing (17 February 2003), they're at the 1.0 beta 1 release. It's gettin' close!

IMHO, this is going to be HUGE. I personally know of several organizations that will be able to use this immediately. I am just excited as heck about this software and what this means. In particular, MSFT should be rather unhappy about this little development. Heh heh heh.