I had this exact issue with a windows 11 operating system. The fix is simple. Quickbooks uses Microsoft XPS Document Writer to send emails through Quickbooks. By default XPS Writer is disabled in Windows 11. All you have to do is enable XPS Writer. To enable XPS Writer navigate to your Control Panel. From the search window inside Control Panel search

" Turn Windows Features On or Off ". Once inside scroll down to the Microsoft XPS Document Writer option. Click the checkbox. It will begin to install the drivers needed for XPS to function. Once you complete the above steps, the Microsoft XPS Document Writer printer will be added or removed from your PC, depending upon your selection.