Aethera
Thekompany.com: information about aethrea, a pim, pdr and messaging application for kde.
http://www.thekompany.com/projects/aethera/index.php3
KDE Pim
K desktop environment homepage, kde.org
http://pim.kde.org/
KNode
K desktop environment homepage, kde.org
http://knode.sourceforge.net/
Thunderbird
Thunderbird
http://www.mozilla.org/products/thunderbird/