We can make an analogy between an e-mail and a postcard: just like a postcard is sent without an envelope an e-mail is mostly sent without a protection to the content; and just like the postman can read the text from your postcard, the guys from your ISP (Internet Service Provider) can read your e-mails. But the things are even worse than that, and here's why: once a postcard is delivered the text written on it may remain only in the memory of the postman, but after an e-mail is delivered a copy of it remains at both your, and your receipt ISP. And most of the time all these emails are stored for years, and anyone (future employers or even stalkers) can read them. And that's not all; in most cases your e-mail passes through more systems, each of them under the control of different people. So even if you trust your ISP and you r receipt ISP (like you may trust your local postman) how can you trust all ISPs from around the world which are located between you two.

Whilst some people are quite happy to have their lives in the open, with their personal details and photographs accessible to anyone on the Internet, some people are a bit more astute. They want to communicate privately with their own friends, but want something more secure than public websites or emails. For them there are two main solutions: encrypting the emails or keep the message on a trusty server where only you and your receipt can read the message. Or even better, you can use both solutions and save the encrypted message on a third-party, trusted server.