hMail Server Alternatives

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

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

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

KerioConnect is a commercial mail and groupware server.

Web-based IMAP email client

Low cost, easy to use Email Server software for virtual, on-premise, or hosted deployments for...

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

Axigen is an integrated email, calendaring & collaboration platform, built on a Linux mail server technology.

Google's encompassing suite of cloud-based business apps.

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.

PowerMTA is an industrial-strength software for high-volume email delivery.

An open source mailserver suite.

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