Do you want to copy attachments from an e-mail directly via drag & drop into Dualoo and this doesn't work? Then most likely you are using Microsoft Outlook to retrieve your e-mails.

Unfortunately, it is not possible to move attachments directly into web applications with Outlook (all other web applications, e.g. Google Drive, are also affected). The reason is the special file system of Outlook and therefore we cannot influence it.

The following three tools (all with costs) solve the problem. The first tool has been tested by us and solves the problem in a very simple and uncomplicated way. It can be tested free of charge for 7 days:

Tool 1: https://outlook2web.com/
Tool 2: http://www.wilutions.com/ddaddin/index.html
Tool 3: http://outlook-drag-drop-to-browser.com/

Source: https://social.technet.microsoft.com/Forums/office/en-US/f55628e6-36ab-444e-bfc0-57df0e323737/drag-and-drop-from-outlook-to-a-browser-based-application?forum=outlook