What email is shown as the "from" address on the Customer's Confirmation email that they receive?

The confirmation and notification emails will come "from" the email address that you have set up in Tools > Online Web Registration > Settings in the Notification Emails field.  If you have multiple Locations with different emails for each Locations, you can have the system use the appropriate email for each, by setting the "Use Location Email if available" box to YES.  Make sure each location has a valid email address under Tools > Edit Settings > Locations.

You may view all notification email addresses in Tools > Edit Settings > Notifications.