Microsoft Exchange replacement

Top Dog in Sight

What the Future Holds

Only a few months old, grommunio is already quite far down the road to becoming a true drop-in replacement for Exchange. Unlike its predecessors, it bundles open source and open standards services and promises to lead the way out of the vendor lock-in jungle. So far, however, admins are likely to be missing more detailed documentation [11] and a full-fledged, automated migration wizard. Grommunio is aware of these shortcomings and is already working intensively on both topics, as the latest updates on the website confirm. Moreover, the migration tools are currently updated frequently.

The Outlook connection (Figure 9) works without problems (Figure 10) but will still have to prove its capabilities in the coming months. The comparatively low prices (see the "Editions" box and Table 1) and the open source character of what is still fairly new software are likely to lower the inhibition threshold for users wanting to try out the groupware product. Extensive independent tests are still outstanding and would be important to back up the vendor's claims relating to speed, stability, scalability, and migration options. If grommunio stands up to the test and the developers deliver the missing features, then grommunio could become a real game changer on the groupware market. The approach definitely looks promising.

Table 1

Features at a Glance

Manufacturer grommunio GmbH
License AGPLv3
Price (per user/month) Community (5 users or fewer) free, Basic (6-49) EUR1.99, Plus (6-49) EUR2.99, Business (50-999) EUR4.49, Enterprise (1000 or more) ask
Operating models  On-premises, cloud
Server OS Linux
Groupware protocols SMTP, IMAP, POP3, MAPI, RPC over HTTP, CalDAV, CardDAV, WebDAV, LDAP, Active Directory, Exchange ActiveSync (EAS), Exchange Cached Mode
Exchange Features
Email Offline mode, public folders, categories and flags, webmail, global address lists
Contacts Support for all contact fields, multiple contact folders, contact groups, export
Calendar Free/busy times, appointment invitations, recurring appointments and exceptions, shared calendars and delegations
Groupware Features
Features Notes, tasks (with time tracking), file synchronization and sharing (ownCloud), chat (Mattermost), video conferencing (Jitsi), office features (OnlyOffice), archive
Clients Outlook (without plugin), all Exchange clients, web GUI, app (chat, video, files), email clients, calendar clients, global search
Architectures High availability, sharding, multidomain, multitenancy, all POSIX-enabled storage back ends, AD forest installations
Security S/MIME, remote wipe, OpenPGP, single sign-on (in development), two-factor authentication (2FA; in development), anti-spam, antivirus (third party)
Administration Features
Installers Installer ISO, OVA, image
Data migration Export from Exchange/Kopano/ICAL/IMAP/POP3 to grommunio
White label/branding Yes
App stores No


Grommunio's free Community subscription provides accounts for five users with basic features such as groupware and mobile device management. The Basic version includes email or web support. Professional users who need telephony support need to purchase the Plus edition. For enterprise customers, the Business subscription has all features, including high availability. Customers who need round-the-clock support have to request this, and it is the only difference between the business and enterprise licenses, apart from the targeted company size. For science, education, public service, government, and NGOs, grommunio grants discounts of up to 25 percent. Hosters can also receive a licensing program specifically tailored to their needs.

Figure 9: After creating users and domains, connecting Outlook users is a smooth process. Microsoft's email client thinks it is talking to an Exchange server.
Figure 10: Outlook users are connected natively in grommunio without a client-side plugin.

The Author

Markus Feilner, technology and network policy editor at, has been working with Linux since 1994. He was deputy editor-in-chief of Linux Magazine and iX and doc team leader at SUSE. He has run his company Feilner IT, specializing in documentation, digital sovereignty, and OSI layers 8, 9, and 10, for 22 years.

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