Kdepim
Kontact is a personal information manager and groupware software suite developed by KDE. It supports calendars, contacts, notes, to-do lists, news, and email. It offers a number of inter-changeable graphical UIs (KMail, KAddressBook, Akregator, etc.) build on top of a common core.
Read more about Kdepim: Differences Between “Kontact” and “KDE PIM”, History, Components