We pass as many details as we possibly can to NAB Transact. The integration options are very limited an email is not an item that is available to us.
We do pass in the "Billing Token" field form the Payment Txn to the Transaction Reference (aka Purchase Order No.) field in NAB Transact.
All reporting should be completed from within Salesforce. This will have all the details you need, including Email address.
The use of NAB Transact login should be in the very rare circumstance of an issue between NAB Transact and Salesforce reconciling.