You don’t need a clearance to use plain old .mil emails. Anything requiring a confidential or above clearance is on a separate network/domain. You are still releasing FOUO (for official use only) controlled information which can become classified higher if combined, but it’s not a spillage on the scale of say Snowden or Trump’s boxes.
Reminds me of how we sometimes export light pollution. When I first got to Afghanistan I thought I would be able to see the stars being in the middle of a desert. That idea was quickly made harder to accomplish by the massive light pollution coming from camp leatherneck which, along with the moon dust perpetually floating mid air, killed any chance to see the stars clearly for miles around. Base turned a patch of desert into a sprawling light factory in just a few years.