To play the devil's advocate, do you expect any privacy with postcards? It is also addressed directly to another person by means of a unique identifier... why i

To play the devil's advocate, do you expect any privacy with postcards? It is also addressed directly to another person by means of a unique identifier... why is email any different? IMAPS et al. is just for the connection between you and your email provider, everything after that is plaintext (till the recipient's email provider gets it.) Now, the interesting question is: is IRS entitled to access emails if both the sender and receiver are using the same provider and it doesn't leave their servers? (I'm guessing the situation is similar to delivering a note by hand through a single third party... again, I wouldn't expect any privacy there.)