I set the option under Archives to preserve the original folder structure. Then the Sent, Trash, etc, folders are retained. I wonder why you want to keep Sent messages separate from other messages? I file my messages together by topic or project, so all related messages, whether sent or recieved, are stored together in their respective folders. All the archiving function needs to do for me is retain all my user-defined folders. To my mind, you want to organize your messages before attempting any form of archiving, and the archiving must preserve accurately what it is given. I don't think the arhiving function should be expected to re-organize your messages and create new folders, which is what you're asking for with your prosposed "Sent Archives|Year" structure.