Reset your DNS configuration for a domain back to the default settings applied by 1&1.
Resetting your DNS settings back to default will cause your domain and E-mail to utilise the 1&1 services.
Ensure you are prepared for the DNS reset before performing the reset. All changes, though live on the 1&1 Server
within minutes, may take up to 1 hour to be fully updated and recognised by all servers/computers on the Internet.