Stronger, bolder, more visually obvious delineation between messages in conversation view. Can't tell where one message ends.
There isn't enough of a visual delineation between messages in conversation view. What is there now is not enough to tell where one message ends and another begins.
Make mails individual "cards" on a background, easily distinguishable from one another.
Header is not prominent enough.
Dividing is not prominent enough.
Names in header are not prominent enough.
I'd second this. On a related topic, I struggle to find attachments on emails that are somewhere in the middle of a conversation view.