"In connection with an unrelated case, the FBI has learned of the existence of emails that appear to be pertinent to the investigation. I am writing to inform you that the investigative team briefed me on this yesterday, and I agreed that the FBI should take appropriate investigative steps designed to allow investigators to review these emails to determine whether they contain classified information, as well as to assess their importance to our investigation," he added.
What is this
“unrelated case”?

While most are thinking this must be something very damaging to Clinton, what if this has to do with Russia’s involvement in hacking, their trying to sway the election, Assange, etc. and …..who knows who else…..

Again the term
"In connection with an unrelated case has me very puzzled.
That could either mean that something was uncovered during an investigation completely unrelated to the FBI’s initial investigation into Clinton’s email server and her and her staff’s handling of secret information was discovered came up with information that proves that she and they willingly mishandled and or covered up the mishandling of classified information or worse, or this unrelated case came up with something that proves something else…..
Whatever this ends up being about, this is some very scary times.
Sometimes I feel like I’m living in real time, something that will be one day written in future history books about the downfall of the American Republic.