$\begin{aligned} I &=\int e^{x}\left(\frac{1-x}{1+x^{2}}\right)^{2} d x \\ &=\int e^{x} \frac{\left(1+x^{2}-2 x\right)}{\left(1+x^{2}\right)^{2}} d x=\int e^{x}\left[\frac{1+x^{2}}{\left(1+x^{2}\right)^{2}}-\frac{2 x}{\left(1+x^{2}\right)^{2}}\right] d x \\ &=\int e^{x}\left[\frac{1}{1+x^{2}}-\frac{2 x}{\left(1+x^{2}\right)^{2}}\right] d x=\frac{e^{x}}{1+x^{2}}+C \end{aligned}$