Cypht with Cyrus IMAP and http://sabre.io/ is the base of WikiSuite's mail stack. As of 2019-09, it is far less feature-complete than Kolab, but it is more tightly integrated. And over time, it will become feature-rich, as is the nature of Tiki's community and development model: Tiki is the Free / Libre / Open Source (FLOSS) Web application with the most built-in features. Please see https://dev.tiki.org/Email-as-a-first-class-citizen
Cypht has what you'd expect from a webmail client, and some very interesting features like aggregating email from multiple accounts.
- Combined inbox, unread, sent, and flagged message views for all your E-mail accounts (and RSS feeds), as well as standard E-mail client folder navigation
- Flexible profiles to combined IMAP accounts with SMTP accounts and setup signatures and reply to details
- Compose messages in plain text, HTML, or Markdown (markdown formatted messages are converted to HTML before being sent)
- Search all your E-mail accounts and RSS feeds at once with a simple form
- Simple interface translation system that does not use gettext or .po files, just arrays of translated strings defined in PHP. Right to left languages are supported.
- Module sets for IMAP, POP3, SMTP, LDAP or local contacts, WordPress, Github, and lots more! Check out the Modules page for a complete list.
- Sessions and user data can be stored in any PDO compatible database or flat files on the server
- Authentication is flexible and currently supports POP3, IMAP, LDAP, an included database schema, dynamic authentication using popular E-mail providers, auto-discovery based on the user's E-mail domain, or you can roll your own with the site module set
- Sessions and Authentication can be customized without breaking any modules using the site module set