I'm a bit confused. On a technical level emails are even less secure than postcards. Everyone involved transporting it, can read, copy and save it. So how are e

I'm a bit confused. On a technical level emails are even less secure than postcards. Everyone involved transporting it, can read, copy and save it. So how are emails private and the most sensitive dataset in the world? I know that my email account is the most important part in my digital life and if someone would get hold of it, I'm basically dead. But the emails I get and send are not private at all.