$\int_0^\infty\int_{ e^{-x}}^1\frac1{x^3y}\,dy\,dx$
$$=\int_0^{\infty}\frac{1}{x^3}\left[\ln y \right]_{e^{-x}}^1dx=\int_0^{\infty}\frac{1}{x^3}\left[0-(-x)\right]]dx=\int_0^{\infty}\frac{1}{x^2}dx=\left[\frac{-1}{x}\right]_0^{\infty}\rightarrow \infty$$