Well, I should say that raw milk does produce SOME mucus, but it doesn't contain the "immune aggravators" that pasteurized milk does. What I mean is that raw milk is structured to be digested easily and is not burdensome to the digestive tract or immune system for almost all people, whereas pasteurized milk has so many things taken out of it and/or manipulated (enzymes, fats, proteins, etc.), that the body has to work extra hard to process it. One of the results of this is often excess mucus production.
Ironically, many people including myself drink raw milk to prevent sickness. This has been done for thousands of years. Most people have been correctly led to believe that they should stay away from dairy during any sort of illness. This is true, but **only of pasteurized milk**. Raw milk, however, is a powerful immune system booster.