There haven't been any policy changes to the email accepted by the Firefox Accounts system. Email addresses that contain Firefox or other Mozilla brands are not rejected. My own account actually has Mozilla branding in it. If the email actually isn't bouncing, there are a couple of common reasons that Firefox may think that the email bounced. Certain email providers seem to send a failure message back to Firefox, even if the email goes through. This is most common (I find) with AOL and Yahoo email addresses. Other than that, vacation replies or other automatic replies that you have setup on your email address can also cause the Firefox Account system to treat it as a bounced email, since it assumes that the automatic reply is an error message. The easiest way to fix this is to temporarily disable any automatic replies. However, I can assure you that it has nothing to do with having the word "firefox" in your email address. Hope this helps.