I'm curious about timelines here. This article states the Dutch notified the US of the intrusions in the summer of 2015, but a lot of emails leaked were from 20

I'm curious about timelines here. This article states the Dutch notified the US of the intrusions in the summer of 2015, but a lot of emails leaked were from 2016. Either the 2016 emails were from a separate hack or the Russians were inexplicably allowed to continue to operate for a full year.