Check the security of your emails
Whenever possible, Gmail protects your info by using Transport Layer Security (TLS) to automatically encrypt emails you send or receive.
TLS doesn’t work with messages from some email services.
If you're on a computer or Android device, you'll know an email is not encrypted when you see the No TLS icon 
Check messages you've received
- Open the Gmail app
.
- Tap a message.
- In the top left of the email, under the sender's name, look for No TLS
If you see the icon, the message you've received might not be encrypted. The sender can find out more by contacting their email provider.
Check messages you're sending
- Open the Gmail app
- In the bottom right, tap Compose
.
- In the "To," "Cc," or "Bcc" field, type your recipient's email address.
- On the right of the "Subject" field, look for No TLS
If you see the icon, the message you're about to send might not be encrypted. Don’t send confidential material, like tax forms or contracts, to that email address.
Why some emails might not be encrypted
For delivery TLS to work, the email delivery services of both the sender and the receiver always have to use TLS. Learn more about email delivery with TLS encryption.
Some email providers can send messages to Gmail users using TLS but don't support receiving encrypted messages.
If you reply to these messages, you might see the red padlock icon even though you're sending from Gmail.
When you compose a message, Gmail tries to determine whether the recipient's email provider supports encryption, and warns you if they haven’t in the past.
This might not be accurate if the message isn’t being sent directly by Gmail. For example, you might see the No TLS icon if you've set up a custom domain name, such as name@yourdomain.com.
Vivian is a Gmail expert and the author of this help page. Leave her feedback about this help page.