The two strongest smells that mayonnaise gives off is egg and vinegar, so you shouldn’t have to worry if your mayo smells like vinegar. Sometimes it can be difficult to tell whether or not mayonnaise has gone bad, so you will therefore have to know what some of the signs are before you decide whether to eat it or toss it out.
If mayonnaise has gone bad chances are it will have a yellowish color which is the result of the egg in it oxidizing. Although mayonnaise usually doesn’t spoil unless it has been sitting around for a very long time, you will still want to be aware of what some of the signs are. It can be difficult to tell if mayonnaise has gone bad by smell alone.