eM Client is a Windows based e-mail client for sending and receiving e-mails, managing calendars, contacts, and tasks.

The Bat! is an email program for Windows that protects the correspondence and empowers the users to handle large amounts of emails quickly and efficiently.

Kontact is a personal information manager and groupware software suite developed by KDE. It supports calendars, contacts, notes, to-do lists, news, and email.

Stoq is an open source framework for enterprise level automated analysis.

AdiInviter Pro is a contact importer and tell-a-friend platform.

Claws Mail is a free and open-source, GTK+-based email and news client. It offers easy configuration and an abundance of features.

SugarCRM is a customer relationship management (CRM) system.

Memotoo sync all your contacts from Gmail, Facebook, phone, Thunderbird, Outlook, etc in a single address book.

Soocial provides a synchronization service that syncs contacts between the users' computers, phones and web apps.

FCorp ID Book is a portable, light but powerful address book.