Thanks for joining the thread, @Ragdavis. I can help you get to the bottom of your emailing transactions concern without a moment's delay.

Regardless if you're using QuickBooks Desktop (QBDT) or QuickBooks Online (QBO), you'll need to have a parent and a sub-customer profile to avoid interchanging your emails. This way, you can also keep track of your income, expense, and balance for each contact accordingly. 

You can either have to choose who's going to be the parent (i.e., contact for sales order) and sub-customer (i.e., contact for invoice) or add a main customer (i.e., name of the company), and both contacts will be the sub-customers.

If you're using QBDT, adding a sub-customer is the same as job costing. To do this, here's how:

1. In the Customer center, highlight the name of the Parent Customer (name of the customer).
2. Click Add New Customer.
3. Select Add Job.
4. Type in the sub-customer's information.
5. Click Ok.

I've attached a screenshot below for your reference.

If you're using QBO, you can either refer to the screenshot below or check out this article for the step-by-step guide: Add and manage customers in QuickBooks Online (Add a sub-customer section). Then, select  Bill with parent or Bill this customer if you want to bill sub-customers individually or as part of the group.

Also,  you can easily keep track of your sales and expenses using predefined customer, job, and sales reports in QBDT. Then, add billable time to your sub-customers when creating invoices in QBO. if you wish to know more about the mentioned processes, you can select the appropriate article below for the QuickBooks product you currently have:

• Customize customer, job, and sales reports in QuickBooks Desktop
• Track Income, Costs, and Profitability By Project

I'm just around to help if you have other concerns about managing your customer profiles and emailing sales transactions in QuickBooks. You can drop a comment below, and I'll make sure to get back to you as soon as I can. Take care always.