I had written an article a while back entitled "Is Microsoft Going Through Your Cloud Stored Files?". Whether the analysis of your content is done by a human, a robot or disgruntled employee, it feels wrong and there are times when you absolutely need to make sure the info in a particular email is secure & protected.
You can always install one of the open source PGP alternatives but require complicated setup and key exchange (which makes these non usable by the average Joe). This is where Mailvelope is hoping to change the industry.
Mailvelope offers free Chrome and Firefox extensions that encrypt outgoing emails via OpenPGP when using the most popular web based email services( Gmail, Outlook.com, Yahoo, etc). Their claim to fame is that it works with the web based clients offered by these services and is super simple to use.
The product is still in beta but has been shown fairly stable during normal use. You install the extension, generate your public and private keys and that's it. The installation walks you through the process and advance computer skills are not required.
Once the keys have been generated, you will see a lock icon in the message compose window [of your chosen email service], by clicking this icon, you can encrypt your message. Remember that to work, the other party also needs a PGP compliant client to decrypt your message and a public key exchange must also occur. The easiest setup is to ensure the recipient also installs Mailvelope.
I would never call encryption easy but this seems to make it simple enough for the general population to use. I will be interested in seeing how they eventually monetize their service.
Encryption icon on a gmail:
How an encrypted message looks
you click on the lock icon and it asks for your private key passphrase