Sending batch emails is such a time saver, and I have an idea that might help. Currently, you can only send an email to one customer at a time in QuickBooks Online. I'd recommend suggesting this feature to our Product Development Team. Our customer’s voice is how change happens! To provide this feedback you can click the Gear icon in the upper-right corner and select Feedback.
You could use your company email provider to send the email promotion in bulk by exporting the Customer Contact List report, which includes your customer email addresses.
Click Reports on the left menu.
Search Customer Contact List.
Click the Export option.
Choose Export to Excel.
This will make it easy to get all the email addresses transferred quickly and get your promos out to your customers. Let me know if you have any other questions, I am just a post away.