Qmail will now be using Rainloop rather than roundcube for webmail. Why do you ask? I have 2 reasons:
1) Rainloop doesn't require mysql which means it is very fast. It does, however, require a database for contacts
2) Rainloop supports mobile devies; IE phones, tablets, etc.
Rainloop has several features you can enable in the admin panel. Take a look at the Rainloop documentation here.