Yahoo error code 421 4.7.0 only appears in the situation of the network congestion. This temporary error fixed itself in a couple of minutes. So whenever this error code prompted on your email account, hold your email activities for a while and then try to sign in again. If that doesn’t give you affirmative results, try reaching out for professional help, as they can guide you at the best and provide a reliable solution. To do so, contact
Yahoo Customer Support ( an online customer helpdesk) via a toll-free number.
