问Nginx提示[emerg] host not found in upstream？

源站：103.213.xxx.xxx bbs.xiaoz.org ，hosts可以访问

serve

        {

        listen          80;

        server_name     bbs.xiaoz.org;

        location / {

           resolver 101.37.xxx.xx;

           proxy_pass http://bbs.xiaoz.org;

           proxy_redirect off;

           proxy_set_header X-Real-IP $remote_addr;

           proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

    }

}