I have been able to set up an automatic forward of all incoming Gmail, but for outgoing I set up a filter, and it doesn't do anything. I need the forwarding to be automatic and discreet.
I am going to try the Gmail Auto-forward script.
You can use the Gmail Auto-forward script bound to a Google Sheet. In Gmail, you create a filter that marks all matching emails with a filter. On the sheet side, specify that label name and the forward address and it will send them automatically.