Roundcube.

open-source webmail-client with modern interface and plugin-architecture

Facts

Axigen
Romanian enterprise email server with webmail, calendar and instant messaging
RO · commercial
↗
EGroupware
German open-source groupware platform with email, CRM, project management and more
DE · open-source
↗
grommunio
Austrian open-source groupware platform as an alternative to Microsoft Exchange
AT · open-source
↗
Kolab
Swiss open-source groupware platform with email, calendar and file management
CH · open-source
↗
Kopano
Dutch open-source groupware platform with email, calendar and video conferencing
NL · open-source
↗
Mailcow
German open-source email server platform with Docker-based installation
DE · open-source
↗
Mailu
Open-source email server in Docker with webmail, anti-spam and antivirus protection
FR · open-source
↗
Open-Xchange
German open-source email and groupware platform for providers and companies
DE · open-source
↗