I am using iRedMail every hour. I have about many instances on many different server over many domains. The accounts are used by different people. My experience shows that users expects:
- Configure SPAM by ownself not only by marking message by SPAM but wants more after some time of using mails. (https://plugins.roundcube.net/packages/johndoh/sauserprefs)
- Desktop Notifications (https://plugins.roundcube.net/packages/kitist/html5_notifier)
- Minimum tasklist or TODO list (they are doing this in drafts whitch is not usable as in external plugin https://plugins.roundcube.net/packages/kolab/tasklist).
I strongly recommends adding those plugins for default instalation package.