How to turn off OneDrive Memories
You can turn off email notifications from the website https://onedrive.live.com/?v=NotificationOptions.
You can also hide the Memories summary in the mobile app by selecting Me > Settings > Personal > Toggle Show photos from this day.
Note: If you see pictures you don't recognize in your OneDrive Memories or On This Day, it is because other apps' folders are included in your device's camera roll. Learn how to stop unrecognized pictures from appearing.