File sound.mp3 and sound.wav should be in /usr/share/roundcubemail/public_html/assets/plugins/newmail_notifier. This causes non-working sound notification.
BTW:
- Also noticed that favicon.ico, mail.png, overlay.ico, newmail_notifier.js are placed in both locations, while they should be only in assets path.
- Also in both locations: markasjunk.js, managesieve.js, password.js, archive.js, acl.js