Thanks for joining the Community today. I'm here to help share some insights about adding a customer name and PO number to the subject line on an email template in QuickBooks Desktop.
Currently, being able to add the customer's name and PO number to the subject line on an email template in QuickBooks Desktop isn't an option for us. Instead, you can enter it manually by adding it to each corresponding email.
Here are some articles that you can also check out about customizing templates for your future reference: