If I receive an MDN and I want to confirm it manually, it warn me that I'm not the official receiver (because it was sent to an alias). If i confirm the MDN, the receiver get also my original e-mail account name which is bad for privacy reasons: Original-Recipient: rfc822;ALIAS@example.com Final-Recipient: rfc822;ACCOUNTNAME@example.com - maybe we can avoid this after setting up alias adresses?
Only leaks if no "SMTP only" account was created for the receiving alias. Maybe a warning text in the popup is a good choice.