This particular issue is only happening to a small number of users on Microsoft email (Hotmail, Live.com etc) boxes. We are not able to replicate the error, so rolling out a fix is taking longer than expected. Please try to disable email sending on your control panel and see if you're still receiving the emails.

yes, this is now fixed for most email services. Hotmail and yahoo is still an issue that should be back to normal in a couple of days.