On reflection, the 'email list' section of a 'contact-centric' view of email would be the sensible place for a 'conversation' email list view. I.e. the email to and from that contact interleaved. In my previous post I'd illustrated the 'contact view' with tabs for emails-from and emails-to that particular contact (which still might be useful) but I should also have considered the 'conversation view' which is simply the same email flows combined onto a single list, sorted by date, with the 'froms' and 'tos' clearly marked. The idea is you see the back and forth communication with that particular person in the correct order.
The mockup screenshot below illustrates the idea, although the actual 'style' of the page would need work. In particular there's a subtlety in that the user might have received an email from the contact by virtue of being on a Cc: list or From:, plus it might be useful to indicate which emails are 'replies' versus fresh 'conversations' - the screenshot below isn't great from a 'style' standpoint but is intended to illustrate the principle. 'Indent' has been use to mark the 'from' emails...
The 'Date' (Datum) column has sort up/down buttons - these might be more important on a 'conversation' view, as it is more natural to see the time flow from top to bottom, while email inboxes tend to be looked at with the newest at the top - this might be an important user preference.
Click to enlarge screenshot: