Create advanced outreach using a power list and map the Sender email and sender name in the advanced outreach participants. Set up the email template to use these in one of the emails
Clone this AO and remove the Power list source and add another that does not have these fields mapped in the participants. When opening the email, it will retain what is selected above even when these fields have not been mapped. When you try to hit save nothing happens. My request is to have some sort of error message that comes up pointing out those two fields.