Bah did the link in my comment not work? I tried updating my original comment to link to http://www.politico.com/story/2015/03/state-department-email... but now there's two versions of my comment, one pre-edit in this chain and one post-edit in another chain I can't find. This article is heavily biased, I think, but it mentions the post Powell rulings. In the Judicial Watch testimony of Cheryl Mills she mentioned the post Powell decisions.
The State Department can't pass laws for which you can be jailed. It can only pass internal rules which it can use to fire you etc. It also cannot produce interpretations or clarifications of laws since only judges do that.
Only congress can pass laws, and so illegal is a strong term reserved for violations of those laws.
There is a case for violating those laws, of course, which is whatever the relevant statutes are for handling secret information under which spies etc are prosecuted.
So while these are internal rules she may have violated, they are not the same as laws, and those laws apply equally to her predecessors, and therefore I feel justified in continuing to make the argument.