Oops ... scratch that ... you want to change the From address ...
While this is not a configurable setting via the Admin you could customize the orders.php class and change the From address ...
Look at the file:
/includes/classes/order.php
around line 999 and 1012 and you will see:
PHP Code:
zen_mail($this->customer['firstname'] . ' ' . $this->customer['lastname'], $this->customer['email_address'], EMAIL_TEXT_SUBJECT . EMAIL_ORDER_NUMBER_SUBJECT . $zf_insert_id, $email_order, STORE_NAME, EMAIL_FROM, $html_msg, 'checkout', $this->attachArray);
PHP Code:
zen_mail('', SEND_EXTRA_ORDER_EMAILS_TO, SEND_EXTRA_NEW_ORDERS_EMAILS_TO_SUBJECT . ' ' . EMAIL_TEXT_SUBJECT . EMAIL_ORDER_NUMBER_SUBJECT . $zf_insert_id,
$email_order . $extra_info['TEXT'], STORE_NAME, EMAIL_FROM, $html_msg, 'checkout_extra', $this->attachArray);
NOTE: classes are cannot be overridden so save the original as well as a copy of your customized file ...