Want to email like a spy on the run? Use Lavabit.
Edward Snowden is apparently using the service, which jumped into existence in 2004 as a result of privacy concerns about Gmail.
"At the time, Lavabit’s founders felt Gmail was a great service but that Google was actively violating the privacy of its users by displaying ads related to keywords in their e-mail," says the Lavabit official website.
So a few Texas programmers with a self-described "maniacal level of dedication" and "experience building mission critical systems" started a company called Nerdshack LLC, which then changed to Lavabit in 2005.
Google's propensity to scan emails for key words and then market that data to advertisers was a clear violation of privacy to the Lavabit founders.
Among other services, the one they offer, and the one Snowden wanted was an encrypted email service that requires a user's password to decrypt. It's called "Asymmetric Encryption."
The short description is that for users of this feature, incoming e-mail messages are encrypted before they’re saved onto our servers. Once a message has been encrypted, only someone who has the account password can decrypt the message. Like all safety measures, encryption is only effective if it’s used.
There's a more in-depth description here, but the simple end-state is that the information is passed through a highly convoluted encryption process that ultimately makes it a massive pain in the rear for agencies like the NSA to decrypt.
"In theory, an attacker with unlimited computing resources could use brute force to decipher the original message," reads the site, "However in practice, the key lengths Lavabit has chosen equal enough possible inputs that a brute-force attack shouldn’t be feasible for a long time to come."