Earlier quoted context omitted.
> You send a clear-text message to a publically-accessible service that is empowered to forward the message to other publically-accessible servers if necessary. This is how postal system works.
Uhh... In the postal system, your message is generally encapsulated in a tamper-evident envelope, carried in locked cars and trucks that enjoy Federal protection against intrusion, and end up in mailboxes that are almost always on private property and/or locked.
That's beside the point though. People in general expect their mail correspondence to remain private, although a motivated third party might be able to defeat security.