I understand your frustration with the drag & drop behavior in Firefox when sending files to Outlook. Currently, Firefox doesn't directly support dragging and dropping files to Outlook as attachments. However, you can easily achieve this by saving the files to your computer first and then attaching them in Outlook. While Opera might handle this differently, I recommend the following steps for a smoother experience with Firefox: Save the files from the web to your computer by right-clicking and selecting "Save link as..." or "Save image as..." depending on the file type. Open Outlook, create your email, and use the attachment button to select and attach the files from your saved location. This way, you'll have the files sent as attachments in your Outlook emails. Feel free to let me know!

That would be a convenient new feature. For now, if you click the little folder icon on the right side of the download, Firefox will launch Windows File Explorer with that file selected so you can copy it (for pasting) or drag-and-drop it.

Mozilla has a product suggestion site at https://connect.mozilla.org/. If you have time, please post this request there to get into the current feedback stream. Use the "Ideas" section of the site.