Most modern encryption products don’t keep the keys that are used to process your message traffic. And some of the newer services are going out of their way to ensure that there is no one – other than you, that is – that has these keys. As an example, look at what Protonmail.com is doing. Proton uses double password protection. The first is used to authenticate the user. After that, encrypted data is sent to the user. The second password is a decryption key and used to decrypt data on your device. Proton never sees that latter key so they do not have access to the decrypted data. On top of all this encryption, they also employ SSL connections so your data is further encrypted across the Internet to and from their servers.
Besides their technology, Proton has established their company outside of the US – in Switzerland actually -- in an attempt to win over customers who may not be comfortable dealing with American-based suppliers. Mailboxes are fixed at 1GB per user, with attachments limited to less than 10 MB. Each mailbox will cost $5 per month.