Thanks for reaching out. Currently it is not possible to attach files from OneDrive as a Copy. You can however use the attach the file as a OneDrive reference link. Please refer to article https://learn.microsoft.com/en-us/graph/api/resources/referenceattachment?view=graph-rest-beta. Please note the above is a beta API and APIs under the /beta
version in Microsoft Graph are subject to change. Use of these APIs in production applications is not supported.
Also please refer to this post https://learn.microsoft.com/en-us/answers/questions/679349/how-to-add-onedrive-files-to-mail-attatchment for info on the topic.
I would suggest posting your query on the raph Feedback forum.
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Thanks.