The best Email Client alternative to Roundcube is Rainloop, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 25 alternatives to Roundcube and 13 are Email Clients so hopefully you can find a suitable replacement. Other interesting Email Client alternatives to Roundcube are Mailpile, Horde, Kolab and SnappyMail.
Simple, modern & fast web-based email client. Modest system requirements, decent performance, simple installation and upgrade, no database required. All these make RainLoop Webmail a perfect choice for your email solution.
Mailpile is a modern, fast web-mail client with user-friendly encryption and privacy features. The development of Mailpile is funded by a large community of backers and all code related to the project is and will be released under an OSI approved Free Software license.
Enterprise-level, browser-based suite for IMAP email, calendar, contacts, tasks, notes, wiki, and file management, offering syncing, shared and unlimited resources, multilingual support, customizable dashboard, and integration with mobile and external clients.
The drastically upgraded & secured fork of RainLoop Webmail Community edition.
All your E-mail, from all your accounts, in one place. Cypht is like a news reader, but for E-mail. Cypht does not replace your existing accounts - it combines them into one. And it's also a news reader :).
Atmail webmail system offers a webmail client, email server platform and mailserver appliance for Linux, Unix and Windows.
Real-time email, chat, audio/video calls & conferences, file-sharing, and contacts app with a modern and intuitive UI.
NexMail is an open-source, modern webmail client designed for self-hosted email servers. Enjoy a clean, intuitive interface with powerful features for managing your emails efficiently.
Microservice based webmail client built with ReactJS and Spring.
Minimalistic webmail client which currently has the main features of any other mail client (read mail, compose mail, organize mail folders...).
NeoMail is a web-based mail client that allows users to access their mail spools and send messages. It does not require a POP3 server, or any shell access for the users. It interfaces directly with user mail spools.
Estonia
EU
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Netherlands
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Bosnia & Herzegovina
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Germany
It's popular, modern programmed, faster than roundcube, but not so feature rich. Much sits below the surface though.