Tools

Ordinary email is far less private than most people think. It usually travels with transport encryption. That protects messages while they move between servers. But the provider still stores your mail in a form it can read. In the past many providers scanned that content to build ad profiles. Transport security is needed. On its own, though, it does nothing to stop the company holding your inbox from reading it.

Two kinds of encryption to separate

'Encrypted email' usually means something stronger. The term covers two ideas worth keeping apart. Zero-access encryption means the provider cannot read your stored mail, because it does not hold the key to your mailbox. End-to-end encryption means only the sender and recipient can read a given message. There is no readable copy on any server in between. A service may offer one, both, or neither. So it pays to know which you are getting.

The split matters because it sets the limits of what a provider can protect. Zero-access encryption guards everything in your own mailbox. It guards it from the provider and from a server breach. End-to-end encryption guards one conversation from everyone except the two endpoints. Strong encrypted-email services give you zero-access storage by default. They add end-to-end encryption wherever the recipient setup allows it.

The leading auditable providers

Proton Mail is the most established option here. It offers zero-access storage, so it cannot read your saved mail. It gives end-to-end encryption between its own users. Its client apps are open source, so the cryptography can be reviewed. And it has a Swiss legal base. That mix of code you can audit and a privacy-friendly country has made it the default pick for people who want private email without becoming cryptography experts.

• Transport encryption protects mail in transit but not from the provider itself
• Zero-access encryption: the provider cannot read your stored mail
• End-to-end encryption: only the sender and recipient can read a message
• Proton Mail and Tuta are the top open-source options you can audit
• No service can end-to-end encrypt a message to a standard Gmail account

Tuta, once known as Tutanota, is another open-source, end-to-end encrypted provider with its own approach. It encrypts not just message bodies but also subject lines and the wider mailbox. It is based in Germany. Its encryption model is built in a different way from Proton's. So it works with the outside world in a different way too. That is a reminder that 'encrypted email' is built in more than one way.

The limit no provider can cross

One limit applies to every service the same way. No provider can engineer around it. No service can encrypt a message end-to-end to someone using a normal Gmail or Outlook account. The reason is simple: that recipient has no key to decrypt it. This is how email built to work across providers behaves. It is not a flaw in any one product. Any vendor who claims otherwise deserves doubt, not trust.

The realistic goal, then, has two parts. First, keep your own stored mail private from the provider through zero-access encryption. That way a breach or a nosy company cannot read your inbox. Second, get true end-to-end encryption with contacts on the same system. For others, use password-protected messages. Seen this way, encrypted email is about cutting exposure in a real way, not chasing an impossible absolute.

What to check before you commit

When you weigh a service, look past the marketing to a few clear signals. Are the client apps open source, and have outside experts reviewed them? What exactly is encrypted - only message bodies, or subjects and metadata too? Where is the company based, and what is its track record on transparency? These questions split services with real, auditable encryption from those that just borrow the word for their brand.

There are trade-offs to accept in return for privacy. Encrypted mailboxes can behave in a different way from mainstream ones. That shows up in server-side search, auto filtering, and integrations, because the provider cannot read your content. For most people these gaps are small next to the gain of a mailbox the provider cannot mine. But going in aware of them prevents letdown later.

Picking the right fit

For most people who want a private mailbox the provider cannot read, Proton Mail is the easiest solid place to start. Tuta is a strong open-source alternative for those drawn to its full-mailbox encryption. Pick the model that fits how you communicate. Set fair hopes about messages to outside providers. Then you will have email privacy far better than the default that ad-funded services offer.