Issue Summary

Dragging email from Outlook to PR attachment deletes it from Outlook

Steps to Reproduce

Steps to Reproduce:
1. Go to the overview tab of a pull request and expand the comment box
2. Drag an email (that you don't mind losing!) into the comment until the paperclip turns into a green check
3. Email is attached to the pull request, BUT is also moved to "Deleted Items" in Outlook

Expected Results

Actual Results

The email get deleted

Workaround

Required, if there is no workaround please state:
Currently there is no known workaround for this behavior. A workaround will be added here when available

Additional Links:
https://developer.mozilla.org/en-US/docs/Web/API/DataTransfer/dropEffect
https://answers.microsoft.com/en-us/msoffice/forum/msoffice_outlook-mso_windows8-mso_2016/drag-and-drop-works-however-deletes-email-can-we/865f60c3-7980-4465-8a19-4d60b0ae5aba