Print Receivables Transactions send email to all contacts email addresses

Summary:

Print Receivables Transactions send email to all contacts email addresses even though it has customer contact defined

Content (please ensure you mask any confidential information):

When an invoice is created with contact and you run the Print Receivables Transaction, the program emails the invoice document to all the email address of the customer's contacts.  So, if the customer has 40 contacts, then the invoice is emailed to all of them.  Is this the way it is supposed to work?  How can we change it so that the invoice will be emailed only to the primary contact or don't send an email at all?