Microsoft Exchange Server

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

Citadel

Is a collaboration suite (messaging and groupware).

KerioConnect is a commercial mail and groupware server.

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

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

OpenChange aims to provide a portable Open Source implementation of Microsoft Exchange Server and…

Secure email with absolutely no compromises. Get your free encrypted email account today.

Linux directory, domain, mail, gateway and infrastructure server for SMBs.

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

EGroupware is free open source groupware software intended for businesses from small to enterprises.

An open source mailserver suite.