Hi, @Jamie Wade
Do not use attachments when adding links in Outlook, add the link directly in the body to send.
The recipient can move the mouse over the link, and if it cannot be opened, there will be a prompt.
Are your OneNote files stored in OneDrive?
File synchronization in OneDrive will be affected by various factors such as network bandwidth, and there will be a certain lag. There is no way to open OneNote files in OneDrive and modify them immediately on desktop OneNote.
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