Linux Softwares to CardDAV

Sunbird was a standalone calendar application and also a Firefox extension developed by Mozilla, designed for managing events, tasks, and calendar synchronization. It aimed to provide a free and open-source solution for personal and professional scheduling needs.

Google Sync was a free service offered by Google to synchronize mail, contacts, and calendar data across multiple devices and platforms. It leveraged various protocols like Exchange ActiveSync, CardDAV, and CalDAV to push updates in real-time, ensuring users had consistent information wherever they accessed it.

iRedMail is a comprehensive, free, and open-source mail server solution designed for ease of deployment and maintenance. It bundles popular components like Postfix, Dovecot, and Roundcube, providing robust email, calendar, and contact management capabilities.

KMail is a powerful and flexible email client tightly integrated with the Kontact personal information manager suite. Part of the KDE ecosystem, it offers robust features for managing your email, including strong encryption options, support for multiple protocols like IMAP, POP3, and Exchange, and seamless integration with other Kontact components like the calendar and address book.

Zimbra Collaboration Suite is a comprehensive open source email and collaboration platform designed for businesses. It provides a secure and feature-rich environment for email, calendaring, contacts, tasks, and file sharing, supporting on-premises and cloud deployments.

Nylas Mail, an extensible open-source email client, offers a unified inbox, robust search, and calendar integration. It supports multiple accounts and provides features like email tracking and undo send, aiming to enhance productivity and email management for users.

Kolab Community is a comprehensive, free, and open-source groupware suite designed for collaborative work. It provides integrated email, calendar, contacts, and tasks functionalities, empowering individuals and teams to communicate and manage their data efficiently and with a strong focus on data privacy.