Landline and email are not secure by any means. If you want secure communications, the transport layer (3G, internet, land lines, postal, talking to people) sh

Landline and email are not secure by any means. If you want secure communications, the transport layer (3G, internet, land lines, postal, talking to people) should always be untrusted and cryptography should be used. However you can only trust one method for the long term which is a pre-shared manual one time pad. Other methods are proven to be somewhat variable in their implementation and ability to remain secure.