Thunderbird Alternatives for Mac OS X

Microsoft Outlook is a personal information manager from Microsoft.

Apple Mail is an email client included with the operating systems macOS, iOS and watchOS by Apple Inc.

SeaMonkey is a free and open-source Internet suite.

Postbox is powerful, intuitive, ultra-customizable, speedy task manager.

Airmail is a fast mail client for Mac and iPhone.

Sylpheed is an open-source e-mail client and news client licensed under the GPL.

Mutt is a text-based email client for Unix-like systems.

Zimbra Desktop is an offline client that lets you manage various email accounts in one desktop tool.

Rambox is a free and Open Source messaging and emailing app that combines common web applications into one.

KMail is the email component of Kontact, the integrated personal information manager from KDE.

Spark is a fast, smart mail manager app.

Polymail is an email application for OS X and iOS known for its clean interface and additional features atop the Gmail platform.

MailMate is an IMAP email client for macOS featuring extensive keyboard control, Markdown integrated email composition, advanced search conditions.