Hi Mark,
Yes, this vertical orientation was intentional. I wanted to emulate Outlook 2003 which I use at home and was enamoured by it.
So far I have not had any feedback on it.
I considered making it an option, unfortunately, I did not know how to do it programatically. If you are a notes programmer, can you help?
Maybe have an option where the use can select : Vertical/ Horizontal Preview pane.