Home » Grommunio

Grommunio

Grommunio — Open-Source Alternative to Microsoft Exchange

General Information
Grommunio is a relatively new name in the mail and collaboration space, but it has been getting attention fast. It’s positioned as a drop-in replacement for Microsoft Exchange and Outlook 365, but built on Linux and open-source components. The idea is simple: give enterprises email, calendars, contacts, tasks, chat, video meetings, and file sharing — all integrated, but without locking into Microsoft’s cloud.

A lot o

Share buttons

Grommunio — Open-Source Alternative to Microsoft Exchange

A lot of admins discovered Grommunio when looking for a way out of high Office 365 licensing bi…

How It Works
Grommunio runs on a Linux server and bundles several services into a single stack: Postfix/Dovecot for mail, groupware modules for calendar and contacts, and extras like chat, video conferencing, and file sync. For end users, Outlook and mobile clients connect via ActiveSync just like they would with Exchange.

The system includes a responsive webmail that mimics the Outlook Web App look. Admins manage everything through a central web console — domains, users, quotas, updates. Multi-tenant mode …

Functions
Feature | What it looks like in practice
—|—
Mail stack | SMTP/IMAP/POP3 backend with Outlook/ActiveSync support
Groupware | Shared calendars, contacts, tasks, notes
Web interface | Modern HTML5 webmail, Outlook-like layout
Collaboration | Built-in chat, video conferencing, file sync
Directory support | LDAP/AD integration for centralized authentication
Security | TLS/SSL, DKIM/SPF/DMARC, antivirus/antispam filters
Multi-tenant | Host multiple domains with separation and branding
Admin console | Web-based central management, monitoring, updates
Licensing | Open source core; enterprise support plans available

Installation Guide
1. Prepare a Linux host (SLES, openSUSE, or Debian/Ubuntu).
2. Add the Grommunio repository and install via package manager.
3. Run the setup tool to configure hostname, mail domain, and admin account.
4. Integrate with LDAP/AD if required.
5. Point DNS (MX, SPF, DKIM, DMARC) to the server.
6. Test with Outlook and mobile clients via ActiveSync.

For larger rollouts, admins often pair it with a load balancer and database replication.

Everyday Use
– Enterprises deploy it as a lower-cost Exchange alternative while keeping Outlook compatibility.
– Service providers host it in multi-tenant mode to offer branded mail and collaboration.
– Public sector uses it for sovereignty reasons — keeping data on national infrastructure.
– IT teams like that they can add chat and video modules without relying on Microsoft Teams.

For users, the difference is barely noticeable: Outlook, phones, and browsers just work as before. For admins, it means updates through Linux repos instead of Microsoft licensing dashboards.

Limitations
Being younger than Zimbra or Exchange, Grommunio’s ecosystem is still smaller. Documentation and community are growing but not as mature. Upgrades can feel rough compared to polished SaaS platforms. Some integrations with third-party SaaS tools are missing. Still, for organizations that value control and cost savings, these are acceptable trade-offs.

Notes from the Field
Admins who tried Grommunio often mention that migration from Exchange feels surprisingly smooth, since Outlook clients connect the same way. A common tip is to test ActiveSync load carefully, as mobile sync tends to be the busiest part of the system. Some teams run it side by side with Nextcloud for a more complete collaboration suite.

Other programs

hMailServer

hMailServer — Lightweight Mail Server for Windows General Information hMailServer has long been a go-to mail server for Windows admins who don’t want the overhead of Microsoft Exchange. It’s free, open source, and delivers the essentials: SMTP, POP3, and IMAP. Nothing fancy, just a solid service that runs quietly once set up.

It’s often deployed in small offices, schools, or as a relay in labs. The attraction is obvious: a small footprint, no license costs, and a GUI admin console that feels fa

Zoho Mail Desktop

Zoho Mail Desktop — Native Client for Zoho Mail General Information Zoho Mail Desktop is the desktop companion to Zoho’s cloud mail service. It was built for one purpose — to give users the same look and feel as the web client, but with offline access and native notifications. It’s available for Windows, macOS, and Linux, and is often deployed in companies that already run Zoho Workplace.

Unlike using Outlook or Thunderbird, there’s no need to fight with IMAP settings or worry about features no

Zimbra OSE

Zimbra OSE — Open Source Groupware Suite General Information Zimbra OSE (Open Source Edition) is the free community build of the Zimbra Collaboration Suite. It’s been around for years as one of the main self-hosted alternatives to Microsoft Exchange. Unlike basic webmail, it includes mail, shared calendars, contacts, and tasks — so it feels closer to groupware than just a mailbox.

A lot of schools, universities, and even municipalities in Europe have adopted it. The reason is simple: no licensi

Zarafa (Kopano)

Zarafa (Kopano) — Open Source Groupware and Collaboration Platform General Information Zarafa was originally launched in the mid-2000s as an open-source groupware server built around compatibility with Microsoft Outlook. Later the project evolved into Kopano, which extended the original mail and calendar features with chat, video meetings, and document collaboration.

It was widely adopted in Europe, especially by organizations looking for an Exchange alternative that could still keep Outlook as

Xeams

Xeams — Spam Firewall and Mail Server in One Package General Information Xeams is a Java-based mail platform that can run in different roles. Some treat it purely as a spam firewall, sitting in front of Exchange or Postfix. Others use it as a full mail server with IMAP and SMTP. The idea is simple: one product that can be adjusted to fit what the site actually needs.

It’s not new in the market, but admins still bring it up when they want something flexible, cross-platform, and easy to manage th

Tutanota

Tutanota — End-to-End Encrypted Email Service General Information Tutanota is one of those projects that put privacy front and center. Based in Germany, it offers a mailbox where encryption is always on — not something users need to enable. Unlike many providers, even subject lines and contacts are encrypted. That detail alone made it stand out when it first appeared and it still does today.

It’s widely used by journalists, NGOs, and people who don’t trust the “free” webmail model. For admins,

Grommunio

Other programs

Main pages

Utility pages

Grommunio

Other programs

Main pages

Utility pages

Submit your application