The purpose of this would be to highlight the last email that I was looking at, rather than the last one I double-clicked.
As things are now, the last email I double-clicked, rather than the last one I looked at, is highlighted.
To keep the present functionality intact, a solution is to add an entry to the email tab's right-click menu that says something like "Display email in list". That would then open a tab displaying the email's account in the usual way (if one is not already open - no duplicates, please), with the email highlighted and the list scrolled so that the highlighted email is visible, say, fifth from the top (this would be configurable).
... View more