Welcome to the Community, @accounts227. 

At this time, the option to consolidate 50 invoices to send in one email isn't available in QuickBooks. However, you can use and create a Statement to send a summary of open invoices to your customer. Here's how: 

1. In the Sales menu, go to the Customer tab. 
2. Select a customer. 
3. Mark the boxes for the (50) open invoices you want to send.
4. Select Statement in the New transaction drop-down located at the upper right of the page. 
5. Choose Open Item in the Statement Type drop-down list. 
6. Enter or select your Statement Date, then click Apply. 
7. Enter the Email address in the field. 

Review the total balance if it's correct. You can also click the Print or Preview at the bottom to see the itemized list. Once ready, you can now click the Save and send button. 

For more information, read through this help article: Create and view customer statements. It also helps you learn about customizing your statements. 

Here are some of our articles that I find helpful to you in the future: 

• Run accounts receivable aging report. It'll help you learn about getting the customer's outstanding balances so you can also send them email reminders. 
• Record invoice payments in QuickBooks Online. Here, you can learn about the different ways of recording payments in QuickBooks. 

Feel free to visit again if you have more questions,@accounts227. We're always around here to guide you more.