THINKERS Alternatives

Zimbra Collaboration is an open, secure collaboration tool for email, calendaring, tasks and more.

A fully fledged, free email server solution, an open source project (GPL v2).

Web-based IMAP email client

Microsoft Exchange Server is a messaging and collaborative software product developed by Microsoft.

hMailServer is a free e-mail server for Microsoft Windows.

An open source mailserver suite.

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.

Kolab Groupware is a secure, scalable, reliable, flexible, full-featured collaboration suite.

Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.

freemium $11.99 / Monthly (Per user - Premium)

Postfix is a mail transfer agent (MTA) that routes and delivers electronic mail.

Modoboa is a mail hosting and management platform including a modern and simplified Web User Interface.

SOGo is groupware server with a focus on scalability and open standards.

Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.

freemium $12.5 / Monthly (Per user - Business Class)