Asp.net drag drop file upload from Outlook and Mac mail

I have an ASP.net Visual Basic website.
On several pages I have an AjaxControlToolkit.AjaxFileUpload.
Most of the time this works for users drag dropping files from folders on their Macs and PCs
But, I want the ability to drag Emails from Outlook and mac Mail, like you can to the windows desktop, onto an uploader and have them uploaded just like normal files
And I want the ability to click on attachments in Outlook or Mac mail and drag those attachments onto the uploader and have those uploaded too, just as if the file had been dragged from the desktop.
I don’t want a browser plugin, because the users might be using any browser.
I don’t want any intermediate steps, like dragging to another folder first.
I do want it to work smoothly on Macs and PCs and with one simple drag and drop action and perhaps an upload click - just like the AjaxControlToolkit.AjaxFileUpload does.

I can't seem to find a way to achieve this. It's as though when you drag drop from a mail program onto a local folder the mail program and the operating system are communicating in some way that they don't when you drag drop onto a webpage.

If what I'm asking can't be done, can anyone explain exactly why it can't be done?

Thank you.