Taking for granted you adhered to generally accepted guidelines, conscientiously, would you care to name the agents, who, in your personal experience, have not acknowledged your query, and thus wasted your SASE?
Naming literary agents who disregard time and effort, causing unnecessary expense, may save some from a useless approach.
To begin the exercise, I name but two: Bleeker Street Associates, and the Gail Ross Literary Agency.
However, if these two, or others to be so named, have respected you, then, let's know that, too.