Thunderbird
Open Source
Thunderbird is a open source mail client developed and maintained by Mozilla foundation.
Apple Mail
Free
Apple Mail is an email client included with the operating systems macOS, iOS and watchOS by Apple Inc.
Airmail
Commercial
Airmail is a fast mail client for Mac and iPhone.
Polymail
Freemium
Polymail is an email application for OS X and iOS known for its clean interface and additional features atop the Gmail platform.
Microsoft Office Outlook
Commercial
Microsoft Outlook is a personal information manager from Microsoft.
Postbox
Commercial
Postbox is powerful, intuitive, ultra-customizable, speedy task manager.
OpenProject
Open Source
OpenProject is a web-based project management system for location-independent team collaboration.
MailMate
Commercial
MailMate is an IMAP email client for macOS featuring extensive keyboard control, Markdown integrated email composition, advanced search conditions.
Compare Spark with alternatives
Compare Microsoft Office Outlook and Spark and decide which is most suitable for you.