size local folders

Can I change the size of the local folders?(mail, left hand side)

if you need to resize the left panel, move your mouse to right side of the panel. Make sure the cursor is at the edge of the panel the cursor should change. It should have two arrows pointing at opposite directions. Click, hold, and drag it inward.

Thanks but I want to increase the size of the folders not the panel

I am sorry, but this is not possible.