This is the rejection error some of the 2FA's are getting. I had the same problem when trying to setup an account with Outlook just now.  This message has been rejected because it has
    a potentially executable attachment "Part 3.eml"
    This form of attachment has been used by
    recent viruses or other malware.
    If you meant to send this file then please
    package it up as a zip file and resend it.