Sidecars.networking.istio.io hosts configuration

Networking
1

Hi, I am exploring sidecars.networking.istio.io and would like to have a configuration to access only one service from another namespace, so i tried the config as below

apiVersion: networking.istio.io/v1alpha3
kind: Sidecar
metadata:
  name: default
spec:
  egress:
  - hosts:
    - "./*"
    - "istio-system/*"
    - "another-ns/another-svc.another-ns.svc.cluster.local"

this does not work, however, I can see the cluster, route, and everything else set properly.
I always get 503: upstream connect error or disconnect/reset before headers. reset reason: connection termination
I tried with also setting the port, but the same error
it only works with

apiVersion: networking.istio.io/v1alpha3
kind: Sidecar
metadata:
  name: default
spec:
  egress:
  - hosts:
    - "./*"
    - "istio-system/*"
    - "another-ns/*"

which is something I do not want.
Any hints on how I can achieve this?