What if the messenger was Anosmic, and the person verifying his identity had a very strong odor. He would never be able to identify the other person by that tra

What if the messenger was Anosmic, and the person verifying his identity had a very strong odor. He would never be able to identify the other person by that trait. Basically, the second person had to have some sort of trait that was easy for other people to see, but not for the messenger. Perhaps colorblindness could have been a factor.