Trying to figure out how to stop a move of Outlook Email during drag and drop. I have tested in your sample code in the Dojo it is also happening there. 

So what is happening is you drag and drop a email, which does work, but instead of making a copy and uploading that it pulls the email out of outlook completely. At first I thought this was a bug in outlook but I tried using the drag and drops of other sites using different browsers and they would not pull the email out of outlook. So I think it is an issue with Kendo UI drag and drop upload. Is this a known bug? Is there a workaround to fix this issue?

Hello,

I am afraid that I am not sure what application or demo you are working with. Could you please provide the live url of the project (if it is a live demo or hosted application) or url with the source code? This way I can go through the code and investigate the described behavior. 

Regards,
Boyan Dimitrov
Progress Telerik

You can see what I mean using the demos provided for kendo ui. I choose to use the doc validation demo but it will happen on any drag and drop upload.

https://demos.telerik.com/kendo-ui/upload/validation

Drag and drop an email from Outlook into the drag and drop area. It will completely pull the email out of outlook. 

Hello Steve,

Thank you for the additional information provided.

I am afraid that the Kendo Upload widget does not officially support drag-and-drop upload of messages from Outlook. Moreover, while reviewing the scenario in question, I noticed that IE 11 and Firefox do not upload any messages dragged from Outlook. Those are uploaded in Edge with no changes in Outlook, while in Chrome, the uploaded messages are removed from Outlook.

Taking into account that the discussed functionality is not present at all for some browsers and the fact that it is not officially supported by the Kendo Upload, I would recommend you to avoid relying on that.

Regards,
Veselin Tsvetanov
Progress Telerik

I ran into this same issue this week. After some research, it turns out that there is known bug in Chrome (Chromium). Specifically, if the drag-effect on the client is "move" instead of "copy".

From the bug report:

<em>What's unexpected here is that DROP_EFFECT_MOVE is the default returned by Chrome in this case, and must be overridden by the app developer by setting dataTransfer.dropEffect = 'copy'.</em>

Here's the Chromium bug report: https://bugs.chromium.org/p/chromium/issues/detail?id=1066975&q=1066975&can=2