Hi there korazy8s,
It's vital that all your transactions are entered correctly for your books to be well balanced. QuickBooks Desktop is a great tool able to help you import transactions from various file types so that they can be added to your books. I can point you in the right direction for help with importing your files.
In order to format your IIF files containing invoices for import, I recommend reading up on this article about importing IIF files. There is the IIF import toolkit in that article that provides info on what can and can't be imported, as well as some example files. For further assistance with these files, I recommend reaching out to the QuickBooks Desktop support team. They'll be able to view the imported invoices in the system with you in order to provide insight into the most effective way to have them marked as email later. You can reach them using the methods outlined in the QuickBooks Desktop support policies.
If you have any other questions, feel free to reach out here.
