Cats always win. They never blink.
Cats blink not with their eyelids, usually, but with nictitating membranes, which, though not voluntarily, moisten their eyes gliding from the inside out. Dogs, birds, fish and many other animals also have these translucent films, which are sometimes called third eyelids.
Now, however many eyelids you have, getting to see email headers is a few mere blinks away at most in Gmail:
›› Get to view an email's every hidden header in Gmail and troubleshoot delivery or display problems, find quirky information or trace the odd unwanted message to its likely origin.