Description
From the 11.37 this release on, Debtor invoice delivery details can now be configured so that, for email delivery, multiple delivery contacts will be grouped onto a single email message if an invoice is emailed to multiple delivery contacts, and the email message that delivers the invoice will be addressed to all delivery contacts.
...
By default, the Delivery Grouping field is set to None so that email delivery of invoices will behave in the same way as prior to v11.34this release. That is, each invoice that is selected on the Billing > Manage Delivery > Delivery screen that is subject to the invoice details will be emailed separately to the delivery contact(s).
...