Don’t Archive Notes
The good news is that there is a simple way for your users to indicate that the notes folder should not be archived.
Go to Compliance Management, then Retention Tags in the Exchange Admin Center.
Add a “Personal Never Move to Archive” retention tag.
Now for the user, go to your Settings and into Options under OWA.
You can then add the “Personal never move to archive” tag.
Return to your inbox and right-click the “Notes” folder to assign the new policy.