Hello!
I occasionally use the Roundcube web interface with my ISP.
I find it visually confusing that the icon for "mark as junk" is a recycling bin, when just next to it is the "red slash" icon that's meant to indicate "trash".
It seems more intuitive to have these switched! Visually, a Recycling bin does not represent "junk" as well as the red slash does because I think most people think of "Junk" as being much worse than trash. The red slash instantly indicates "Keep away" or "do not touch," which I think is more applicable to junk mail than trash.
Just my two cents as a graphic & web designer.
Thanks for the work you do!
Kristin P
Hillsboro, OR