Gmail warning "Be careful with this message"

What it means

Gmail sometimes shows a banner above an email, such as "Be careful with this message", "This message seems dangerous" or "Gmail could not verify that it actually came from example.com". A yellow banner means "suspicious", a red one means "probably dangerous".

For an honest sender, the cause is almost always the same: Gmail could not prove the email really came from your domain. SPF, DKIM or DMARC failed or are missing, so your real email looks like a fake.

Why it matters

• Many readers will not click a link, open an attachment or reply when they see this banner.
• The same problem that triggers the banner also pushes emails into spam, or gets them rejected.
• Other causes exist: a link to a site flagged as harmful, a dangerous attachment type, or a From name that imitates a known brand.

How to check

Delivmail checks this for you in two ways:

• Send a test email: on the home page, copy your unique test address, send it a normal email from the mailbox you want to check, then open the report.
• Use the Domain scanner: type your domain at /domain-scanner to read your DNS records without sending anything.

In the report, look at the SPF, DKIM and DMARC lines first, then at the blacklist section for the domains in your links. In Gmail itself, open the email, click the three dots and choose Show original: the top of the page shows SPF, DKIM and DMARC as PASS or FAIL.

How to fix it

1. Make sure SPF passes for the server that sends the email. Add any forgotten tool (newsletter, shop, website) to your single SPF record.
2. Turn on DKIM in your mailbox provider and in every sending tool, using your own domain, not the tool's default domain.
3. Publish a DMARC record, even a gentle one:

   v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com

4. Check alignment. The domain in the visible From address must match the domain that passes SPF or DKIM. A newsletter tool signing with its own domain is a common cause.
5. Check your links and attachments. Remove links to blacklisted domains or URL shorteners, and avoid sending .exe, .js or macro-enabled Office files.
6. Do not imitate other brands in your sender name, for example "PayPal Support" on a domain that is not PayPal's.

If only some people see the banner

The message may have been forwarded, or the recipient marked your earlier emails as spam. A forwarded email can lose SPF; DKIM survives forwarding, so make sure every email is DKIM-signed.

Check that it is fixed

DNS changes are not instant. Most are visible within a few minutes, but some providers take up to 24 to 48 hours.

Send a new test email from the home page: SPF or DKIM should pass and DMARC should pass. Then send a real email to a Gmail address you control: the banner should be gone. Gmail's own advice is in its Email sender guidelines.