The Context: I'm setting up a new Linux PC (Mint OS). I logged into Yahoo Mail using Firefox and clicked on the browser notification in the corner that said something like "Make Yahoo the default for mail links". The Problem: When I click Mailto links in Firefox it takes me to a broken Yahoo Mail page. The page says "Your mail is temporarily unavailable" when that is not the case - Yahoo Mail works when I manually browse it. Further details: I confirm that the "Applications" section of Firefox settings shows Yahoo mail as the default for mailto links. And specifically, the application details specify that the url used is: https://mail.yahoo.com/mrd/mail/any/compose?src=mailto&url=%s