Rsync enabled but authentication failure

how to allow rsync connections? start the service but access fails

Sorry, you must be more specific. For example: Rsync on your sever to backup data from your laptop requires you to have rsync running in daemon mode on your laptop; a connection may fail if your laptop is not running when your server requests the connection/access.

You’re right

I’ve created a specific machine-rsync account and added it to the wheel-group. With that I was able to access /mnt/pool0/ of my NAS