Hello Vikas Lokhande,
Thank you for reaching out to Microsoft Support!
After testing, the draft email will be automatically deleted when it is sent, so when we manually delete the email, there will be an error 404. You can try to GET the draft email through GET message request, if 404 appears, it means that the draft has been deleted, or you can log in to Outlook. Check in the Drafts folder.
GET https://graph.microsoft.com/v1.0/me/messages/{id}
Hope this helps.
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