You can block customers from receiving invoices through InExchange Invoice Printer if you for example don't want to invoice a specific customer through InExchange.
To do this you'll have to print an invoice to the invoice printer that's made payable to customer in question. After logging in and coming to the stage Select how to send you invoices, mark the customer with your mouse pointer and right-click. Choose the alternative Block customer to block them from receiving invoices through InExchange.
The customer will then be marked red and the error message The customer is blocked will be shown when you drag your mouse-pointer over the red marking to the left of the customer.
To remove this block you simply need to right-click on your customer again and choose Block customer again to unmark this.