I think you've both misinterpreted my comment. All I was envisaging was being able to simply append the existing email text/formatting into a note of your choice. The OneNote mention was illustrative of the process to select the appropriate note, nothing more.
FactMan's point regarding email chains is valid, though this is basically true of any documentation system and I'd agree that automating this would be a massive undertaking which would likely not satisfy everyone (personal preferences, "see below" responses, organisational differences, replies to only one person, etc.). Whilst I'd l