By definition, mailto
uses whatever mail client is configured in the user's browser, and sends from their own email address. (From the spec: "Originator fields like From ... when present in the URI, MUST be ignored.")
If you have a web server somewhere, a better solution would be to avoid mailto
entirely. Instead, have the QR code direct the user to a page on your server. The server script for that page (written in, say, PHP) would send you the email. Then, it would also serve up a confirmation message to the user.