Emails between two .gov accounts may not be any more secure

than between a private email account and a .gov account.

Which is a reason why, depending on how her server was set up, Hillary's use of private email might not have reduced security.

http://www.politico.com/story/2015/03/hillary-clinton-address-email-controversy-115903.html

The fact that Obama corresponded with Clinton via a private server stoked fears that the arrangement increased the risks that either of them could have been hacked or that messages between them could have been intercepted more readily than communications between two “.gov” email accounts.

However, cybersecurity experts said that was not necessarily the case, since communications between government e-mail servers handling unclassified information are not always encrypted or directly connected.

“There is no top-level, [Office of Management and Budget]-driven, thou-shalt-run a common-network-with-a-common-backbone, which is what we were trying to get years ago, but could just never do it,” said one expert who worked on cybersecurity issues in the George W. Bush White House and asked not to be named. E-mails “could go directly from one to another, but that depends on those two [agencies’ technology leaders’] getting together and engineering some kind of cross-connect.”

The former official said that proposals over the last decade to create a government-only network went by the wayside.

“The grand idea of connecting the entire federal government on fiber that’s only for the government – that’s about as practical as building a highway system that’s just for the government. Way too expensive to install, maintain and operate. So then you fall back on, okay, we’ll use commercial fiber,” the official said.

SNIP