Apple Mail Alternatives for Mac OS X

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.

Microsoft Outlook is a comprehensive personal information manager designed for managing email, contacts, calendars, and tasks.

Postbox is a powerful and customizable email client designed for professionals managing high volumes of email. It offers robust features for organizing, searching, and managing multiple accounts efficiently, enhancing productivity through a clean interface and advanced tools.

Airmail is a powerful and lightning-fast email client designed for macOS and iOS. It aims to provide a clean, modern interface with advanced features for managing multiple email accounts efficiently.

Mutt is a highly configurable, text-based email client for Unix-like systems. It offers powerful features for advanced users who prefer a lightweight and efficient email management experience directly from the command line.

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.

OpenProject is a powerful, web-based open-source project management software designed for teams of all sizes. It offers comprehensive tools for managing projects, tasks, teams, and communication in one centralized platform. Ideal for organizations prioritizing collaboration, flexibility, and data control.

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.

Open365 is a comprehensive, open-source productivity suite offering cloud storage, office applications, and communication tools. Built upon a foundation of open-source technologies like KDE, Seafile, and LibreOffice, it provides a robust alternative to proprietary solutions, emphasizing privacy and control.

Spark is a powerful and intelligent email client designed to enhance your productivity and streamline your inbox management. It offers a range of features like smart inbox organization, email scheduling, and integrations with popular services, making it a comprehensive solution for busy professionals and individuals alike.

Polymail is an advanced email client for macOS and iOS, built to enhance productivity for professionals using Gmail. It goes beyond basic email functions with robust features like email tracking, scheduling, and team collaboration tools, all wrapped in a sleek and intuitive interface.

<p>MailMate is a powerful, keyboard-centric IMAP email client for macOS designed for users who demand advanced email management capabilities and a highly customizable workflow, featuring strong Markdown integration and robust search features.</p>