Hi there, donna119.
QuickBooks Online (QBO) uses one email address (Company Email) when sending transactions such as purchase orders. Thus, the option to set up an email per user is not possible. In the meantime, I encourage you to visit our QuickBooks blog. From there we share the latest QuickBooks news and feature updates of the product.
Find out more about managing purchase orders in QBO through the following article: Create and send purchase orders in QuickBooks Online.
You might want to visit the following link to become more familiar with the features and functions of QBO:
Be sure to drop me a reply if you have additional questions. I'd be more than happy to help. Stay safe and have a good one.