I filed the following issue when I tried switching to RoundCube: http://trac.roundcube.net/ticket/1486568#comment:3
...which as just been closed with a wontfix. Fair enough, bug trackers aren't the place for discussion, so I'm here as I'm curious what the design decision/objection is to letting users save their sent mails into their Inbox?
Saving into the inbox is how I use my email account so threaded views display in context, without it RoundCube isn't a viable option for me, which is a shame, as it's a very nice client.
Admittedly, it also seems to be missing a threaded view, but that's another issue.
List info: http://lists.roundcube.net/dev/