When attempting to download a file from email from MasterCook I am getting an unconfirmed crdownload file.
This issue is not specific to MasterCook. In fact, it happens to thousands of people who do not even have MasterCook. Your web browser either did not fully download the file or it didn't properly rename the file after it fully downloaded it.
You can simply try changing the file extension from .crdownload to .exe and then open the file.
Otherwise, see these articles below or research the error message online to find more solutions.
CRDOWNLOAD File Extension - What is a .crdownload file and how do I open it? (fileinfo.com)
What Is a CRDOWNLOAD File? (And How to Open One) (lifewire.com)
Edge downloads save as CRDOWNLOAD files - Microsoft Community