A good way to prevent passive mass surveillance of your messages and emails is to use a website such as https://privatebin.net or https://privnote.com. These services encrypt your own self-destructing messages locally in your browser to be sent to your intended recipient.
It should be noted that third party websites should not be trusted to encrypt sensitive information. Both of the listed websites also use JavaScript to encrypt your messages, which is notoriously awful when it comes to exploits and vulnerabilities.
Everyone’s threat model looks different. I personally only use this to relay information that is not overly confidential (in case the websites are compromised), my recipient does not use a trusted encryption method (such as PGP), and that I feel the surveillance on all members of the conversation is passive enough that we will all view and destroy the message before any adversary will have a chance to read it.