When possible, Gmail protects your info by automatically encrypting your emails, which turns them into a code during delivery. This security tool is called Transport Layer Security (TLS) and helps prevent others from reading your emails.
If you're on a computer or an Android device, emails that aren't protected by this security tool will show No TLS . This icon looks like an open red lock and means that someone else might be able to read the email.
On your iPhone and iPad, your emails won't show No TLS . To send and receive messages securely, follow these security tips.
Why some emails might not be encrypted
For this security tool to work, the email providers of both the sender and the recipient always have to use TLS. Learn more about email delivery with TLS.
Some email providers send messages to Gmail addresses using TLS but can't receive encrypted messages.
If you reply to these messages, this icon could show up even though you're sending from Gmail.
Sometimes you'll get a "No TLS" warning even if a message is protected by encryption, like when:
- Encryption hasn't worked for a certain email provider in the past
- Gmail isn't directly sending the message. For example, this icon might show up if you've set up a custom domain name, such as email@example.com.