Citadel, EGroupware, and SOGo are all free, open-source, self-hosted groupware servers built for organizations that want to run their own email, calendar, and…
Best for: Small teams or hobbyist admins who want a lightweight, all-in-one self-hosted messaging server (email, forums, wikis, IM) on modest hardware and are comfortable with its unique rooms-based interface.
Freemium / Open Source · From Free (Community Edition); paid cloud plans from EUR 21.90/month
Best for: Teams that need groupware plus project management, CRM-style tracking, and file sharing in one open-source suite, with the option to skip self-hosting via EGroupware's own eCloud plans.
Best for: IT teams that want standards-based email, calendar, and contacts sync (CalDAV, CardDAV, ActiveSync) integrated with existing LDAP or Active Directory infrastructure at production scale.
At a Glance
Citadel
egroupware
SOGo
Primary category
Collaboration
Collaboration
Collaboration
Rating
Not documented
Not documented
Not documented
Pricing model
Free / Open Source
Freemium / Open Source
open-source
Starting price
Free
Free (Community Edition); paid cloud plans from EUR 21.90/month
Free
Free plan
Not documented
Yes
Not documented
Free trial
Not documented
Not documented
Not documented
Platforms
Web
Web, iOS, Android
Web, iOS, Android
Team collaboration
Not documented
Not documented
Not documented
AI features
Not documented
Yes
Not documented
Public API
Yes
Yes
Yes
Standout Differences
Broadest feature set
EGroupware bundles project management, InfoLog CRM-style tracking, integrated file management, and video conferencing integration on top of core groupware, going well beyond email and calendar.
egroupware
Standards-based sync
SOGo natively supports CalDAV, CardDAV, and Microsoft ActiveSync, giving it broad compatibility with Outlook, Thunderbird, and mobile mail clients out of the box.
SOGo
Longest operating history
Citadel's codebase dates back to 1987, giving it one of the longest continuously maintained histories among self-hosted messaging servers, written in C for a low-resource footprint.
Citadel
Deployment flexibility varies
EGroupware is the only one of the three with an official managed cloud edition (eCloud); Citadel and SOGo are self-hosted by default, though SOGo has an official commercial support partner in Alinto.
egroupware, SOGo, Citadel
Feature-by-Feature
Core Messaging
Feature
Citadel
egroupware
SOGo
Email hosting
Available
Available
Available
Shared calendar
Available
Available
Available
CalDAV and CardDAV sync
Not documented
Not documented
Available
Microsoft ActiveSync (mobile)
Not documented
Available
Available
Directory and Collaboration Extras
Feature
Citadel
egroupware
SOGo
LDAP / Active Directory integration
Not documented
Not documented
Available
Project management
Unavailable
Available
Unavailable
Wikis, forums, and team chat
Available
Available
Unavailable
Deployment and Support
Feature
Citadel
egroupware
SOGo
Official managed cloud/SaaS option
Unavailable
Available
Unavailable
Commercial support available
Unavailable
Available
Available
Pricing Compared
Starting price reflects the lowest paid tier, not the full cost for every team size or usage level.
Citadel
Open Source (Self-Hosted) — Free N/A
egroupware
Community Edition — Free N/A
eCloud — EUR 24.90/month Monthly, 2-user minimum
EPL Smart — From EUR 62.50/month Monthly, 10-user minimum
eFlat School — EUR 1,295/year Annual
Universal / eFlat — Custom (price on request) Annual
SOGo
Self-Hosted (Open Source) — Free N/A
Commercial Support (via Alinto) — Custom pricing Contract
Pros & Cons
Citadel
Pros
Completely free and open source under the GPL, with no paid tiers or vendor lock-in
Unifies email, forums, calendars, wikis, and messaging in one self-hosted server instead of many separate tools
Long, continuously maintained project history dating back decades, indicating stability of the core codebase
Written in C for a lean, low-resource footprint suitable for modest hardware
Cons
Requires self-hosting and server administration skills; there is no managed hosted version
Rooms-based architecture is a distinctive but unfamiliar paradigm for users coming from mainstream email/chat tools
No commercial support organization or SLA; support relies on documentation and community forums
Smaller active user and developer community compared to mainstream groupware platforms
egroupware
Pros
Fully-featured Community Edition is free and open source under the GPLv2 with no artificial limits
Can be self-hosted for full data control, or run as EU-hosted cloud SaaS
Broad feature set covering email, calendar, files, projects, and helpdesk in one suite
Modular design lets organizations enable only the apps they need
Cons
User interface feels dated compared to newer SaaS collaboration tools
Self-hosting requires ongoing server administration and update management
Enterprise-tier and cloud pricing require contacting sales or reading tiered per-user documentation
Smaller ecosystem and community than larger open-source rivals like Nextcloud
SOGo
Pros
Free and open source with no per-user licensing cost for the core server
Broad native client support through CalDAV, CardDAV, and ActiveSync
Integrates with existing LDAP, Active Directory, and IMAP infrastructure
Proven at scale in production environments with thousands of mailboxes
Active commercial steward (Alinto) available for organizations that want paid support
Cons
Requires in-house IT expertise or a paid support contract to install, secure, and maintain
Web interface looks dated compared to modern SaaS email clients
No official cloud-hosted SaaS version directly from the core project, only third-party hosting
Documentation can be technical and geared toward system administrators rather than end users
Use Cases
Choose Citadel: Small teams or hobbyist admins who want a lightweight, all-in-one self-hosted messaging server (email, forums, wikis, IM) on modest hardware and are comfortable with its unique rooms-based interface.
Choose egroupware: Teams that need groupware plus project management, CRM-style tracking, and file sharing in one open-source suite, with the option to skip self-hosting via EGroupware's own eCloud plans.
Choose SOGo: IT teams that want standards-based email, calendar, and contacts sync (CalDAV, CardDAV, ActiveSync) integrated with existing LDAP or Active Directory infrastructure at production scale.
Citadel
Self-hosted organizational groupware — Small organizations or communities run Citadel to get email, calendaring, and forums from one self-hosted server instead of separate tools.
Privacy-focused community hosting — Privacy-conscious operators use Citadel to run their own email and discussion infrastructure without relying on third-party SaaS providers.
egroupware
European data-sovereignty-conscious collaboration — Organizations that must keep email, calendar, and file data on EU soil use EGroupware's self-hosted or German-hosted cloud options instead of US-based SaaS suites.
Nonprofit and school administration — Nonprofits and schools use discounted eCloud NGO or flat-rate eFlat School plans to run email, scheduling, and file sharing on a fixed annual budget.
Self-hosted Microsoft 365 alternative — IT teams that already manage their own servers deploy the free Community Edition to replace proprietary groupware licensing costs.
SOGo
Self-Hosted Business Email — Small and mid-size businesses replace hosted email suites with a self-hosted SOGo server for full control over data and infrastructure.
ISP and Hosting Provider Webmail — Hosting providers deploy SOGo to offer webmail, calendar, and contact services to thousands of customer mailboxes across multiple domains.
Exchange Alternative for Regulated Industries — Organizations with data residency or compliance requirements use SOGo to keep email and calendar data on infrastructure they control.
Frequently Asked Questions
Which of Citadel, EGroupware, and SOGo is easiest to self-host?
Citadel is the leanest to run, being written in C for a low-resource footprint, while SOGo and EGroupware are more feature-rich but require more setup, such as configuring LDAP or Active Directory integration for SOGo, or enabling only the modules you need in EGroupware's modular suite.
Is there an official cloud-hosted option so I do not have to self-host?
EGroupware is the only one of the three with an official managed cloud edition, eCloud, starting at EUR 24.90 per month. Citadel and SOGo are self-hosted by default, though SOGo can be run through third-party hosting or with commercial support from Alinto.
Do these tools sync with Outlook and mobile devices?
SOGo explicitly supports CalDAV, CardDAV, and Microsoft ActiveSync plus Outlook and Thunderbird plugins. EGroupware includes mobile sync as a listed feature. Citadel's support for these specific sync standards is not detailed in available documentation.
Which tool is best if I also want project management or CRM features, not just email?
EGroupware, which includes InfoLog task and CRM-style tracking plus project management alongside core groupware. Citadel and SOGo are more narrowly focused on messaging and calendaring.
Can I get paid support if something breaks?
SOGo has an official commercial support partner, Alinto. EGroupware's paid cloud and enterprise tiers typically include support. Citadel has no commercial support organization, relying on documentation and community forums.
How mature are these three projects?
Citadel is the oldest, dating to 1987, followed by EGroupware (2003) and SOGo (2004). All three have long, continuously maintained histories as self-hosted groupware options.