The company, or any middleman, can read your messages if they have the keys. In many services, the keys come from the company. EEE is only as trustworthy as the clients and processes you use.
You can pick any. I guess the way is to just pick one based on it's description or users or package availability or size and then learn to use it. And or try another one when you figure out if it has problems. Sick with the one you like the most. Or write your own.
Yes. Email is also pretty thoroughly broken after years of spam and corruption by Microsoft and Gmail. It was never a reliable system and is even less so today. It's a good idea to try again and use different systems if you have some.
This exactly. It's more like a firewall for your browser. Because web browsers are incredibly crap software that's pretty completely ignored privacy and filtering along their development and it's being slowly patched on in tiny kludges and extensions instead of being set in policy from the start.
Of course spam and malware is a hard problem in web browsers. It's been a hard problem everywhere else, too.
The company, or any middleman, can read your messages if they have the keys. In many services, the keys come from the company. EEE is only as trustworthy as the clients and processes you use.