iRedMail
A fully fledged, free email server solution, an open source project (GPL v2).
20 Alternatives To iRedMail
Apple Mail
There’s big news attached.
G Suite
Google’s encompassing suite of cloud-based business apps.
Horde
Horde Groupware is a free, enterprise ready, browser based collaboration suite.
Mail-in-a-box
Mail-in-a-Box provides webmail and an IMAP/SMTP server for use with mobile devices and desktop mail software and also includes contacts and calendar synchronization.
Mailbird
Mailbird is the best email client for Windows 7, 8 and 10
Mailpile
Mailpile is a modern, fast web-mail client with user-friendly encryption and privacy features.
Microsoft Exchange Server
Microsoft Exchange Server is a messaging and collaborative software product developed by Microsoft.
Outlook
Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
Postbox
The Power Email App for busy professionals, like you.
ProtonMail
Secure email with absolutely no compromises. Get your free encrypted email account today.
Rainloop
RainLoop is a web based email client.
Roundcube
Web-based IMAP email client
SOGo
SOGo is groupware server with a focus on scalability and open standards.
Sylpheed
Sylpheed is a simple, lightweight but featureful, and easy-to-use e-mail client (mailer, MUA).
Zimbra
Zimbra is trusted by over 500 million users to increase productivity with a complete set of collaboration tools while maintaining total control over security and privacy.
Zimbra Collaboration Suite
Zimbra Collaboration is an open, secure collaboration tool for email, calendaring, tasks and more.
Zoho Mail
Zoho Mail is a webmail service built with the needs of a modern business in mind.
Zoho One
Zoho is an all-in-one online office suite.
eM Client
eM Client is a Windows-based email client for sending and receiving emails, and managing calendars, contacts and tasks.
mailcow dockerized
An open source mailserver suite.