Is it possible to fix/dock the preview pane so that it's always there? The modern monitors are all very wide so there's plenty of space horizontally. Having the preview pane disappearing and appearing again when you click on an email message in another folder or list is very annoying. 

I would like to ask your UI designers to understand that Zoho Mail can be used for work. The less nice "popping up" panels and other "cool' things, the better. The interface shouldn't be overly volatile, this is very distracting. Why don't just fix the damn thing in one place, what's the point of making it sliding to and fro?