Hello there, KingTours.

Allow me to join the thread and provide additional information regarding the email Subject line for sales forms in QuickBooks Online (QBO).

The Subject line that you set on your template will be applied to all the sales forms you use. However, if you wish to have a different subject line for each transaction for your customer, you can easily modify the subject line before sending the email.

If you encounter any issue while sending sales forms to your customers and want to know how to resolve it, you may find this article helpful: Fix the Delivery Server Down error in QuickBooks Online.

Let me know if you have further questions when emailing your sales forms. I'm here to answer them for you.