The Hillary Rodham Clinton e-mail controversy points out this irony: It's hard to say exactly what a secretary of state's e-mails are. Are they diplomatic communications? Or more like letters? Or both?

Last week, it emerged that as secretary of state, Clinton used a single private e-mail address and a personal server for all of her e-mail, official and un.

At a Tuesday news conference at the United Nations, Clinton said that she had been at fault and that "looking back, it would have been better for me to use two separate phones and two e-mail accounts," but "it didn't seem like an issue" at the time.

Clinton said she combed through about 60,000 of her e-mails as secretary, half of which she sent to the State Department. Those other 30,000? Yoga, Chelsea's wedding, personal stuff, so she hit Delete: "I had no reason to save them."

Reince Priebus, chairman of the Republican National Committee, said that since she did the deleting, "no one but Hillary Clinton knows if she handed over every relevant e-mail." The House committee on Benghazi, delighted, will haul her in.

No laws were broken, but it looks bad. "I mean, a personal server," says Ross Baker, professor of political science at Rutgers University. "I know of no mortals who have a personal server." Transparent it isn't.

To be fair, the divide between personal and official is often obscure. "It may be a hopeless metaphysical task to separate things that are official from things that are purely private," says Baker. "I'd hate to be given the task of seeing which of the 60,000 e-mails fall comfortably into one category or another."

In the last week, we've learned that just about everybody in government mixes official and personal. Just about everyone else does, too. A memorable 2013 Forbes survey found that 64 percent of workers visit a non-work-related website while at work. About 29 percent spend one to two hours, and 21 percent two or more, doing that.

Not to defend Clinton - "I can't imagine why a secretary of state would do this," says Baker. But we live in a culture in which e-mail is, literally, beneath our active notice. It's an old technology (around 30 years old for many of us), part of the wallpaper, nothing special. Most workers move without much thought from personal to business and back. Save that report, click; browse TMZ, click; send that spreadsheet, click; Facebook, click-click.

Heather LaMarre, assistant professor of political communication at Temple University, says, "Politicians are still struggling to understand how to communicate effectively in a digital age." They're caught between the need to look good in public and the illusion of private space in e-mails. "They haven't figured it out," LaMarre says, "because our culture hasn't figured it out."

We users of e-mail, LaMarre says, "have created a culture in which we expect our e-mail to be private, when it isn't. We insist on thinking of it much as we once thought of letters."

But as secretary of state, shouldn't Clinton have been more careful? "These are fair questions," says Mark Lashley, professor of communications at La Salle University. Work in a government office, he says, made it clear to him that he worked in the public eye. All of us do - and few of us keep that in mind.

"People often don't grasp who might potentially see the things you put out there," Lashley says. "I see this with students, older people, people in all walks of life. Whether it's a Web page, blog post, e-mail, texting . . . it's somewhere someone else could access it, legally or not."

E-mail is intimate. Marketing blogger Perry Marshall calls it "THE most intimate of all mass communication media. Far more intimate than a website, or Facebook, or Twitter, or even Text Messages." As with handwritten letters or phone calls, there's a sense of immediacy, personal connection in a private space, the disembodied presence of the other person with you. And for most of the 100 billion-plus e-mails sent every day, nobody else cares. Nobody's going to look.

But they could. And, despite all of the political careers gone smash from unwise e-mail, we forget. "We see these as things that could never happen to us," Lashley says. "Besides, it's all so quickly written and sent, and so easily forgotten within minutes." Thus, a cabinet member deletes her yoga e-mail.

Both too controlling (make all e-mails private, when you can't) and insufficiently wise (it looks bad), Clinton's actions may help her critics create "a narrative in which she is evasive or secretive," says LaMarre, "and that could be what hurts her most."

215-854-4406 @jtimpane