Hillary Rodham Clinton may have been right to snub the State Department's e-mail system.

Clinton's use of a private e-mail account while secretary of state has raised concerns that her communications may not have been secure. But the State Department's cyber infrastructure could use an upgrade of its own -- in fact, many of the agency's links to the online world were down Friday, including parts of the unclassified e-mail system.

"As a part of the Department of State's ongoing effort to ensure the integrity of our unclassified networks against cyber attacks, the Department is implementing improvements to the security of its main unclassified network during a short, planned outage of some internet-linked systems," spokesperson Jen Psaki said in a statement.

But it's unclear just how planned the outage was. One agency employee who requested anonymity because he was not authorized to speak publicly said neither he nor his co-workers were aware of the outage in advance. The same thing happened last November, he said, when State's unclassified e-mail system was shut down for days -- apparently because of concerns about hacking.

Senior officials at the time confirmed that technicians at the agency had detected "activity of concern" on parts of the system handling unclassified e-mail -- although they insisted that classified systems were not compromised.

The agency declined to answer questions about how long Friday's outage had been scheduled or when it would end. But Psaki said the agency's classified systems remained secure. "The Department continues to closely monitor and respond to activity of concern on our unclassified network," she said. "Such activity is something we take very seriously."

There are some government-wide guidelines for securing computer networks, but best practices can vary greatly because IT decisions are generally made at the agency level. And despite being an agency that deals broadly with sensitive foreign relations topics, the State Department's efforts are falling short, experts say. The State Department had one of the lowest cybersecurity assessment scores among major federal agencies last year, according to the latest Federal Information Security Management Act report. 

"The State Department definitely has some work to do," said Jonathan Mayer, a computer scientist and lawyer affiliated with Stanford Law School's Center for Internet and Society.

In the State Department's congressional budget justifications for fiscal year 2016, the agency wanted $10 million for a "cyber enhancements" program that appears aimed at fixing security holes and bringing systems up to date. The improvements would include "the necessary re-architecting of the classified and unclassified networks that offers additional protections and mitigates known security vulnerabilities," the document reads. It also notes that the funding would support replacement of "obsolete operational infrastructure" with technology built for current IT architecture standards.

Carol Morello contributed reporting for this story.