Cypht is a webmail client which supports JMAP (and IMAP of course) that was added to Tiki Wiki CMS Groupware version 20.0
Cypht with Cyrus IMAP and http://sabre.io/ will be the base of WikiSuite's mail stack. It will be less feature-complete than Kolab at first, but it will be much more tightly integrated. And over time, it will be feature-rich.
https://dev.tiki.org/Cypht-integration
https://doc.tiki.org/Tiki20#Webmail
https://cypht.org/