Implicit in your post is the assumption that NSA actually has the emails now.
Given the current tyranny, there is a very strong likely hood NSA was ordered at gunpoint to destroy all traces
Very possible, even probable. However, the people in the NSA have also no-doubt seen the odd disappearances and "accidents" that surround obama and Clinton. We're only talking about a few GB of data. Something that would easily fit on a thumb drive or two. Data that no-one wants to officially admit exists is easy to officially ignore and/or copy when everyone wants you to erase the logs and any trace of it. If the NSA personnel have any common sense, there are multiple copies of that tucked away in odd places, and some very direct sealed letters waiting in their lawyers files marked "just in case."
Given the Obola-Holder-Clinton-Soros-Lynch administration, I would go the other way around.
The NSA and DOD and ALL other intell agencies would be FORCED to delete all the email information it had, but the BATF/DHS/FBI - and everybody else doing “background checks” for gun purchases would be triple backed up, and the paper copies kept as well in each agency!