Thanks for joining this thread, @Gayle920.
I appreciate you sharing on-point details about emailing your receipt.
Currently, there isn't an option to change the file name from Cash Sale to Donation Receipt when emailing a sales receipt to customers.
As an alternative, you'll need to manually save it as PDF and email it outside the program. Here's how:
I'd also like sharing this article so you'll be able to learn more about the program: Help Articles for QuickBooks Desktop.
Don't hesitate to leave a comment below if you have other concerns. I'll be around to help, @Gayle920. Take care always!