A red open lock in Gmail warns about unencrypted email delivery. It is a reason to check the message’s security before sending sensitive information. It is not, by itself, proof that the sender is an attacker or that your entire Google Account has been compromised.
Check the message’s security details
Gmail normally uses Transport Layer Security, or TLS, for email transfer when both mail providers support it. On a computer, open a received message and expand Show details next to the recipient. Check the security information, such as standard TLS encryption or no encryption supported.
When composing, use the available Message security control to inspect protection for the intended recipient. Do not confuse the browser’s HTTPS connection to Gmail with the separate transfer between email providers. A secure browser connection does not establish that every email delivery hop used TLS.
Consider the specific warning
Google says a message may be unencrypted if a sender’s provider does not support TLS. Its guidance also notes that warnings can appear where encryption has failed for a provider previously or when sending from a custom domain. Read the actual message details instead of making a conclusion based only on the icon’s color.
For received sensitive information, notify the sender through an established channel. For a message you are about to send, pause and agree on an approved protected route. Do not resend private data merely as a test of whether the warning disappears.
Choose a response appropriate to the account
A work or school administrator can investigate domain routing and applicable encryption policy. Provide the affected domain and non-sensitive security details. A personal Gmail user cannot force another provider to support TLS by changing a local browser setting.
Do not turn off protections, accept an insecure mail-server configuration, or send credentials in plain text to work around the warning. Confidential mode is also a separate access-control feature, not a universal repair for transport security.
After the delivery route has been corrected, verify the security details for a new appropriate message before relying on it for sensitive communication.
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References
Reviewed against the linked official and developer guidance on October 27, 2026. Available options and screen labels can vary by account, device, region, and organization policy.