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Roundcube
Two decades of continuous development made Roundcube the standard-bearer of open-source webmail - a PHP IMAP client that gives any mail server a polished, application-like interface in the browser. It connects to whatever IMAP/SMTP stack you run - Dovecot, Postfix, a hosted mailbox - and delivers the full desktop-client experience: drag-and-drop message management, threaded conversation views, full MIME and HTML mail handling, find-as-you-type address book with groups and LDAP connectors, multiple sender identities, full-text search, and spell checking in dozens of languages. The default Elastic skin is genuinely responsive, working as well on a phone as a desktop, and the entire UI is skinnable. The plugin API is where deployments get shaped: managesieve exposes server-side filter management in the UI, enigma brings PGP encryption and signing via GnuPG, markasjunk trains spam filters, zipdownload batches attachments, password lets users change credentials, and attachment_reminder catches the classic forgotten-attachment email - among hundreds of community plugins. Built-in caching keeps large mailboxes fast, IMAP ACLs and shared folders support team setups, and XSS protection is engineered into the rendering pipeline. It scales from a single personal mailbox to unlimited users, backed by MySQL, MariaDB, PostgreSQL, or SQLite. GPL-licensed with regular security releases.
Benefits
- Any Mailbox, One Interface
- Connects to any IMAP/SMTP server - your own Dovecot stack or hosted mail - with a consistent UI.
- Email Without the Data Mining
- Your messages render on your server with no ad profiling or inbox scanning.
- Two Decades of Maturity
- Battle-tested code, regular security releases, and an ecosystem of hundreds of plugins.
- Works on Every Screen
- The responsive Elastic skin delivers a full client on desktop, tablet, and phone.
Features
- Desktop-Class Mail Handling
- Drag-and-drop management, threaded views, full MIME/HTML support, and multiple identities.
- Address Book with LDAP
- Find-as-you-type contacts, groups, vCard import/export, and directory connectors.
- PGP via Enigma
- Server-side GnuPG encryption, signing, and key management in the webmail UI.
- Sieve Filter Management
- Build server-side mail filtering rules visually through the managesieve plugin.
- Plugin API and Skins
- Hundreds of extensions and fully customizable theming without touching core code.
- Built for Scale
- Mailbox caching, IMAP ACLs, shared folders, and unlimited users on standard databases.