How do I send a Mass Email in Quickbooks Enterprise?
You can use a professional SMTP relay service to do so. Once you are approved to use that service, you will just need to configure your SMTP settings in QuickBooks Enterprise to send email through it.
Go to your customer list by clicking customer. There is a small box to the left where you can select a customer and a small box at the top to select all. Select them. Click batch actions and send your email.
You can use this way to sent a mass email in QuickBooks enterprise. Hopefully this answer will help you and if you need any further information and have queries regarding QuickBooks just contact through QB- QuickBooks Online Support.