When you attach a file from your OneDrive account to an email message, by default, the recipient will be given a link to the online file, which may cause some difficulties if the recipient hasn’t been given permission to the file or if the recipient is outside of the university. To bypass potential problems, you can attach a copy of the file to the message.
Note: If you choose Computer in step 4, you will be given the option to upload to OneDrive and share as a link or to attach as a copy.
Add a OneDrive attachment to a message in Outlook Web Access (OWA)
Add a OneDrive attachment to a message in Outlook for Windows