I could not find any supject that already coverd this feature but if I´ve missed one, I´m sorry.
I would love to be able to reply to an email right in the email (preview) window. English is not my native language so I´m trying to explain what I mean.
I use the reading panel on the right. So if I get an email I click on it and I can read it on the right (without opening it in an additional window). If I now press the reply button an addidtional window opens the email and the reply panel.
In outlook if your press the reply button the reply starts right in the reading panel on the right. No additional window is beeing opend. You can push an button to undock the reply and then have your additional window but you can also just write your replay in the reading panel and sent it from there.
I like this workflow and use it nearly all the times. Only on rare occassions I actually undock the reply and have it opend in an new window.
I´d like to see this feature implemented