Scheduling Invoice Email Delivery
You can use the Apex Scheduler to run InvoiceEmailDeliveryScheduler class to schedule email delivery of invoices on a regular basis. Invoices that are not auto-approved, cannot be emailed as part of the Invoice Runs. You might also not want to email invoices as soon as they are generated. For sending such invoices through email, you can schedule this batch job to run at a weekly or monthly frequency.