Nylas Mail Alternatives for Linux

Thunderbird is a free, open-source email client developed by the Mozilla Foundation, offering robust features for managing multiple email accounts, integrated chat, and RSS feeds. Known for its extensibility and focus on user privacy and security.

Evolution is a comprehensive personal information manager for the GNOME desktop environment, designed to manage emails, contacts, calendars, and tasks. It provides a unified interface for various communication and organizational needs.

Mailspring is a modern, fast, and free desktop email client for Mac, Windows, and Linux. It offers a beautiful interface, powerful features like unified inbox, email tracking, and broad platform support for an enhanced email experience.

Geary is a modern email client designed for the GNOME desktop, emphasizing a conversational view for streamlined email management. It offers a clean interface, supports multiple accounts, and integrates with the GNOME environment to provide a cohesive user experience for organizing and sending emails.

Zimbra Desktop provides a unified interface for managing multiple email accounts, calendars, tasks, and contacts offline. It supports various protocols like IMAP, POP, CalDAV, and CardDAV, offering a comprehensive personal information management solution.

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.