Kontact is described as 'is the integrated Personal Information Manager of KDE' and is an app in the Office & Productivity category. There are more than 100 alternatives to Kontact for a variety of platforms, including Windows, Mac, iPhone, Online / Web-based and Linux. The best alternative is Google Calendar, which is free. Other great apps like Kontact are Microsoft Office Outlook (Paid), eM Client (Freemium), Apple Mail (Free) and Microsoft Mail and Calendar (Free).
With Google Calendar, its easy to keep track of all your lifes important events in one place. You can add events and send invitations effortlessly, share your schedule with friends and family, and search for events you might enjoy.
Postbox is an email application that helps you organize your work life and get stuff done. It has all the elegance and simplicity of Apple Mail, but with more power and flexibility to manage even the most demanding workloads.
Google Contacts is Google's contact management tool that is available in its free email service Gmail, as a standalone service, and as a part of Google's business-oriented suite of web apps Google Apps.
MyLifeOrganized (MLO) is a personal task outliner and to-do list manager which will help you to organize your goals, projects and tasks into a tree. The To-Do list with actions that require immediate attention will be generated.