It is highly unlikely that someone can get food poisoning from eating mayonnaise, simply because there are so many additives put in as preservatives that it is difficult for bacteria to grow. Unless you allow your mayonnaise to sit out in a warm place in an opened jar over a very long period of time, it is highly unlikely that you will suffer food poisoning from eating it.

You should however pay attention to the expiration code on the jar that you get from the supermarket, just so you will know around how long you will have to eat it. Even after the expiration date it is usually still acceptable to eat it. And while leaving a jar of mayonnaise outside of the refrigerator does not usually cause food poisoning, it does tend to adversely affect the texture of it.