Nothing makes you 100 percent safe, Miller said. Encryption keys can be compromised, "key sniffers" can be surreptitiously installed on your computer, and don't even think about using your work computer to check your personal e-mail.
"They own the computer you're sitting at," Miller said. "They're probably going to be in even better shape to [look at your personal e-mail]."
Chris Swenson, director of software industry analysis at NPD, however, believes that simpler steps to protecting your computer and yourself may be better than all-out e-mail encryption.
"The leading security software does a very effective job of protecting your computer against [spyware]," he said.
Updated software, a secure wireless connection and backed up files will be enough for most users, Swenson said.
But for Miller, even that isn't enough. The bottom line? Make it as secure as you can and hope for the best, Miller said.
"Raise the bar high enough and hope they move on to the next guy," he said. "That's true for computer security in general."