It cannot get to room temperature. If at room temperature, then two hours is the maximum, after which bacteria will grow very quickly.
Dr. Doyle debunks the mayonnaise myth. Mayonnaise can be left out for a long time without causing sickness HOWEVER certain microorganisms can make the mayonnaise not taste as good this however will NOT make you sick! I'm assuming the mayonnaise is store bought and not made at home otherwise it's entirely different.