I can see that linking an emailed invoice with Trustpilot is a great idea.
Currently, the feature that you're looking for is unavailable. QBO allows integration with a number of third-party apps and software that can help you . You can go to our QuickBooks Apps website and search for this link: https://zapier.com/apps/quickbooks/integrations/trustpilot as a sample app.
Since there's no automatic way of connecting email with the said platform, I encourage you to submit feedback to our Product Development Team. This way, our developers can consider adding the said option in future product enhancements.
Here's how to send feedback:
Click the Gear icon at the top, and then choose Feedback.
Enter your comments or product suggestions, like "I'd like to link my emailed invoices with trustpilot."
You can also attach a photo to emphasize your concern, and then select Next.