Please be advised that the updating of email addresses provided by QuickBooks support does NOT work if you utilize the "Projects" or "Sub-Customer" features for your Customers.  if you do use the "Projects" or "Sub-Customer" features for your Customers, any email address changes you make in the Client profile will NOT automatically populate when you are building new invoices.

The email address in the root Customer account is correct BUT once you attempt to create an invoice for a "Project" or Customer "Sub-Account", the email address in that new invoice will revert to a single email address listed in the root Customer account.

This is a software issue shared with multiple QuickBooks technical support individuals over the past 3-6 months and no effective solution has been made to users except a work around which includes the manual updating of all email addresses when building new invoices while utilizing Projects or Sub-Accounts.