Hi rbarreca,
Thank you for feedback and I can see how helpful for you and your business to be able to make the subject title of a emailed purchase order change from the standard to Purchase order. I have forward this to our relevant team to let them know of the feature you're looking.
You can send your feedback through your QuickBooks account through Settings icon, and select Feedback. Our Product Team will review on this for you for consideration.
Feel free to message us back if you have any other questions. Have a great day!
