I tried all sorts. Nada.
In the end, I had to do the same thing as CarlB56, with a little nuance.
Environment: Windows-7 Ultimate Edition, Office 2007, iTunes 12.3.0.44, iPhone 6 Plus, iOS 9.0.2
- In "Settings"->"Mail, Contacts, Calendars"->"Accounts"->[MyEmailAcct]-> Make sure the "Notes" button is set to Green (button to the right).
- In Outlook I highlighted all my Notes.
- Right click and selected "Moved to Folder"
- I selected the "New" button.
- Entered "NotesBkup" in the "Name" field and hit "OK"
- Here's where Outlook got weird ... it popped up a warning dialogue saying it might take some time to move the items, which I "OK" acknowledged. BUT, instead of copying/moving the Notes to the new folder, it copied them to all to a Mail Draft as Attachments! Go figure.
So then I just did what Carl did.
- For each Note, I created a "New" Note in Outlook, then I did Copy/Paste from the Note attachment in the email draft, to the new Note in Outlook.
- Once I'd reproduced each Note, I then re-synched the iPhone6Plus ... all Notes properly synched this time.
- I test-edited a Note on the iPhone and re-synched with iTunes. It synched the change.
- I test-edited a Note in Outlook and re-synched with iTunes. It also synched that change.
Important observations: It didn't make duplicate Notes entries, it didn't scramble any, and it didn't lose any. So, I guess I declare this issue resolved, using CarlB56's solution. Kudos Carl ... lose 200 House Points, Apple, and send the engineer responsible to detention with Professor Snape.