23 open-source Business Email & Groupware vendors
Open-source software for Business Email & Groupware that you can self-host, with auditable source code — regardless of the developer's headquarters.
- vendors scored
- 23
- European
- 16
- foreign-owned
- 2
- last checked
- 11 October 2026
Vendors, scored
Score per vendor: 0 = high exposure, 100 = sovereign
Sort
- Sovereignty score 94 out of 100Benno MailArchivGermany · Self-hosted / open sourceGerman, audit-proof enterprise email archiving system for GDPR/GoBD-compliant storage of millions of emails, integrable with any email/groupware system. Developed by LWsystems GmbH (Bad Iburg); core and web app under AGPLv3, some modules proprietary.
- Sovereignty score 94 out of 100CipherMailNetherlands · Self-hosted / open sourceAmsterdam-developed open-source email encryption gateway that centrally enforces S/MIME, PGP and PDF encryption for all outgoing organisational traffic, acting as a mail proxy between the firewall and internal mail server.
- Sovereignty score 94 out of 100DovecotFinland · Self-hosted / open source · owner in GermanyOpen-source IMAP and POP3 server from Finland (Dovecot Oy), part of German Open-Xchange since 2015. High-performance storage and synchronisation of email within enterprise networks.
- Sovereignty score 94 out of 100EGroupwareGermany · EU sovereignGerman open-source groupware platform with email, CRM, project management and more
- Sovereignty score 94 out of 100grommunioAustria · Self-hosted / open sourceAustrian open-source groupware platform as an alternative to Microsoft Exchange
- Sovereignty score 94 out of 100MailcowGermany · Self-hosted / open sourceGerman open-source email server platform with Docker-based installation
- Sovereignty score 94 out of 100MailuFrance · Self-hosted / open sourceOpen-source email server in Docker with webmail, anti-spam and antivirus protection
- Sovereignty score 94 out of 100ModoboaFrance · Self-hosted / open sourceOpen-source mail server platform by NGYNLABS of Nantes, France, released under the ISC licence and self-hosted.
- Sovereignty score 94 out of 100MoxNetherlands · Self-hosted / open sourceModern, Go-based single-binary mail server (MIT licence) that sets up email authentication (SPF, DKIM, DMARC) out of the box. Developed by Mechiel Lukkien (Amsterdam, Netherlands), co-funded by NLnet; no controlling company.
- Sovereignty score 94 out of 100Open-XchangeGermany · EU sovereignGerman open-source email and groupware platform for providers and companies
- Sovereignty score 94 out of 100Proxmox Mail GatewayAustria · Self-hosted / open sourceOpen-source email security solution (AGPLv3 with commercial subscriptions) from Austria's Proxmox Server Solutions GmbH, acting as a mail proxy between the internet and the internal mail server against spam, viruses and phishing. A distinct product from the better-known Proxmox VE virtualisation platform.
- Sovereignty score 94 out of 100RadicaleFrance · Self-hosted / open sourceLightweight open-source CalDAV and CardDAV server (calendar and contacts, GPLv3), ideal for decoupling from Google/Apple cloud sync. Originated at French web consultancy Kozea; no controlling company in the classic sense, community-maintained.
- Sovereignty score 94 out of 100RoundcubeSwitzerland · Self-hosted / open source · owner in Germanyopen-source webmail-client with modern interface and plugin-architecture
- Sovereignty score 94 out of 100SOGoFrance · Self-hosted / open sourceOpen-source groupware with ActiveSync compatibility and web interface
- Sovereignty score 94 out of 100Tine 2.0Germany · Self-hosted / open sourceGerman open-source groupware suite (email, calendar, contacts, CRM, HR/personnel management, file sharing) developed and sponsored by Metaways Infosystems GmbH, based in Hamburg. Tine 2.0.Org community edition is licensed under AGPLv3; Metaways offers commercial support, managed hosting (tine20.com/tine20.net), and enterprise editions. Actively maintained as of 2026 with a live commercial offering.
- Sovereignty score 90 out of 100KolabSwitzerland · EU sovereignSwiss open-source groupware platform with email, calendar and file management
- Sovereignty score 79 out of 100EximUnited Kingdom · Self-hosted / open sourceFlexible and highly configurable open-source Mail Transfer Agent, originating at the University of Cambridge (UK) and widely used in complex enterprise environments for advanced email routing. Community-maintained, no controlling company.
- Sovereignty score 79 out of 100iRedMailChina · Self-hosted / open sourceOpen-source mail server installer that sets up a full mail environment (SMTP/IMAP/POP3/webmail) within minutes on RedHat, Ubuntu or Debian. Developed by a Chinese company (iRedMail Information Technology Co., Ltd.).
- Sovereignty score 79 out of 100Stalwart MailUnited Kingdom · Self-hosted / open sourceModern open-source email server written in Rust with JMAP support
- Sovereignty score 71 out of 100Cyrus IMAPUnited States · Self-hosted / open sourceRobust, community-maintained enterprise mail and calendar server, suited to organisations with tens of thousands of concurrent users. Originally Carnegie Mellon University (US, 1993); now governed by an independent, mainly US-based governance board, no controlling company.
- Sovereignty score 71 out of 100Mail-in-a-BoxUnited States · Self-hosted / open sourceOpen-source project (public domain, CC0) that sets up a complete, turnkey mail server appliance, including DNS, SPF, DKIM and Let's Encrypt. Created by Joshua Tauberer (Washington DC, US); no controlling company.
- Sovereignty score 71 out of 100PostfixUnited States · Self-hosted / open sourceThe de facto open-source Mail Transfer Agent (MTA), originally written by Wietse Venema while at IBM's Watson Research Center (US). No controlling company; maintained individually, the foundation of millions of self-hosted mail servers worldwide.
- Sovereignty score 71 out of 100ZimbraUnited States · Non-EU vendorEnterprise email and groupware platform with calendar, contacts and tasks
Assess your own stack in the assessment
Assess your stack →