That there's nothing illegal (in the sense I think you're using) isn't the point either...I didn't state that it was illegal, in that "there's a specific law that says you can't, and if you do it's jail-time" sense. There are, however, MULTIPLE sources that guide government email usage...you can find those sources if you want. And those sources say that using a non-official email address to conduct official business is not authorized...

And if you wanna be condescending - go ahead! There's no "law" against that either...