Gmail > See all settings > Forwarding and POP/IMAP > Add a forwarding address > Next > Proceed > OK

Gmail > See all settings > Filters and Blocked Addresses > Create a new filter > 'Size greater than 0 Bytes' > Create filter > 'Never send it to Spam' + {'Always mark it as important' || 'Forward it'} > Create filter > OK

Repeat the second step for the email address specified in the 'Forward it' field.
