Hello all,

As per Amish's reply, you can see that a possible workaround for the "delete" issue is the dropEffect to be set to "copy" in the dropover event:

• https://answers.microsoft.com/en-us/msoffice/forum/all/drag-and-drop-works-however-deletes-email-can-we/865f60c3-7980-4465-8a19-4d60b0ae5aba 
• https://www.telerik.com/forums/paste-files-into-radupload-dropzone#-joHU82nXUysw0gggoszQw 

<script>
    // apply to all RadAsyncUpload controls on the page
    function pageLoadHandler() {
        $telerik.$(".RadAsyncUpload").each(function (ind, el) {
            var au = el.control;
            if (au.get_loadedModuleName().toLowerCase() == "file api") {
                au._uploadModule._dropoverHandler = function (ev) {
                    var dt = ev.originalEvent.dataTransfer;
                    dt.dropEffect = "copy";
                    // we need to call prevent default, otherwise
                    // the browser will try to open the document (by default)
                    ev.preventDefault();
                    ev.stopPropagation();
                }

            }
        })

        // Sys.Application.remove_load(pageLoadHandler);  
    }
    Sys.Application.add_load(pageLoadHandler);
</script>
<telerik:RadAsyncUpload runat="server" ID="RadAsyncUpload1"></telerik:RadAsyncUpload>

Regards,
Peter Milchev
Progress Telerik

Hello all,

I will try to summarize and add recent news.

Microsoft has a bug report where the drag of the messages to any non-Microsoft browser (meaning Internet Explorer or old Edge) is not supported:

• https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/212440/;
• https://feedback.telerik.com/aspnet-ajax/1373106-add-ability-to-drag-and-drop-files-and-messages-directly-from-outlook-to-radasyncupload;

Nevertheless, you might see this "working" in new versions of Google Chrome and the new Edge. This is due to some commits that Microsoft made to the Chromium core, which will be used in the new Chromium-based Edge browser.

• https://www.windowslatest.com/2019/02/28/drag-and-drop-support-to-chrome-for-attachments-from-outlook/;

The glitch with this implementation is that the dragged message will be uploaded properly in the browser but it will be moved to the Deleted folder in Outlook.

With that said, we might need to wait for Microsoft and Chromium teams to implement the correct message upload and then the AsyncUpload might be able to properly handle the message drag and drop directly from outlook.

In the meantime, the only tested cross-browser solution is to drag the message/attachment on the file system and then upload the files.

Regards,
Peter Milchev
Progress Telerik

The issue seems to be a Microsoft limitation and it is marked as Won't fix in their tracking system here-
https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/212440/

Hi guys,

Unfortunately the current level of technologies makes implementing this feature impossible because the browsers don't treat mails dragged from outlook as files. If this behavior changes in the future we will add support for it.

Regards,
Telerik team