How can I avoid Gmail security warnings on emails?
Updated on 18 Oct 2026: We clarified Gmail warning types, corrected sender requirements, and added fixes for encryption and attachment warnings.
To reduce Gmail security warnings on emails, authenticate every sending domain with SPF, DKIM, and DMARC, make sure at least one passing authentication method meets DMARC's domain alignment requirements, inspect links and attachments, and build sender reputation gradually. Gmail still makes the final call, and authentication alone does not guarantee warning-free delivery.
A 'Be careful with this message' banner is a safety signal rather than a single error code. Gmail evaluates authentication alongside message content and sender behavior. Read the explanation beneath the banner before changing DNS or copy, because a sender verification warning needs a different fix from an unsafe attachment or an encryption warning.
- Authentication: Configure SPF and DKIM for each sending source. DMARC passes when at least one passes with the required domain alignment.
- Links: Every link should point to a domain you control or trust, without odd redirects, compromised pages, or mixed branding.
- Message intent: Messages asking for passwords, payments, urgent account action, or sensitive data need extra care.
- Testing: Compare the affected message with tests sent to separate recipient accounts. A same-address test alone does not establish why Gmail displayed a warning.
Match the fix to Gmail's warning
Gmail uses several security warnings, and they do not share one fix. Record the exact banner wording, open the message details, and preserve the original headers before changing the campaign. A question mark beside the sender or a statement that Gmail could not verify the sender points to authentication. A phishing, attachment, or account activity warning points to a different investigation.
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Could not verify sender or question-mark avatar | Gmail could not authenticate the message | Gmail's Authentication-Results and the visible From domain |
Scam or phishing warning | Suspicious request, link, or sender behavior | Link destination and account history |
Attachment warning | Blocked, infected, or unscannable file | File type, archive, and scan result |
Red open padlock or no encryption | The message lacks transport encryption | TLS support on the sending SMTP server |
Suspicious account activity | A Google Account sign-in or security event | Recent security events and connected devices |
Gmail warning clues and the first check to make
A recipient marking a verified message as safe is feedback to Gmail, but it does not repair authentication, a risky URL, or an unsafe attachment. Correct the source issue before resending. Do not ask recipients to bypass a warning without verifying the message.
For an account access warning, open your Google Account directly and review recent security events and devices. If the activity is unfamiliar, follow Google's account recovery steps, change the compromised password, remove unfamiliar access, and enable 2-Step Verification or a passkey. DNS changes do not resolve an account takeover.
Fix authentication first
The first place to check is domain authentication. Gmail wants to know that the domain shown to the recipient has authorized the system sending the message. SPF checks whether the sending server is allowed by the envelope sender domain. DKIM checks whether the message has a valid cryptographic signature. DMARC ties the visible From domain to SPF or DKIM through domain alignment.
Passing SPF for an unrelated platform domain does not satisfy DMARC, and the same applies to DKIM signed with an unrelated domain. DMARC needs only one passing method with domain alignment. Under relaxed alignment, billing.example.com and example.com share the same organizational domain; strict alignment requires identical domains. Google's authentication guidance also explains why authenticated messages still need content and reputation checks.
A message can show a familiar From address and still fail the identity test. For Gmail, the important question is whether the sending path proves that the visible From domain authorized the message.
Under Google's sender guidelines, all senders to personal Gmail accounts need SPF or DKIM, valid forward and reverse DNS, TLS, standards-compliant messages, and a reported spam rate below 0.3%. Bulk senders need SPF and DKIM, a DMARC record (p=none is sufficient), and DMARC domain alignment for direct mail. Marketing and subscribed messages also need RFC 8058 one-click unsubscribe headers and a visible unsubscribe link in the body. Use RSA DKIM keys of at least 1024 bits, preferably 2048.
Google's bulk-sender FAQ counts close to 5,000 messages or more to personal Gmail accounts in 24 hours across the same primary domain and its subdomains. Bulk status is permanent once assigned. Dividing campaigns among subdomains does not avoid the requirements.
Basic DMARC record for monitoringDNS
Host: _dmarc.example.com Type: TXT Value: v=DMARC1; p=none; rua=mailto:dmarc@example.com
Start at p=none when you need visibility, then move toward quarantine or reject after your legitimate sources are passing. DMARC uses relaxed SPF and DKIM alignment by default. Set strict alignment only when your mail design requires exact domain matches. Suped's DMARC monitoring groups report data by sending source so you can investigate legitimate senders with authentication failures before changing policy.
Suped DMARC dashboard showing email volume, authentication health, and source breakdown
Also check the sending platform setup itself. Most email platforms provide DKIM DNS records and support a custom return-path domain. Enable signing after publishing the records, then verify the DKIM-Signature d= domain on a delivered message. If SPF is your DMARC passing method, configure a return-path domain that meets your From domain's alignment requirements.
If the warning appears only after forwarding or mailing-list delivery, inspect the final Gmail copy rather than the original send alone. Forwarding can break SPF, and mailing lists can modify content that DKIM signed. Compare Authentication-Results and ARC evidence before changing the original sender's DNS.
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What's your domain score?
Deep-scan SPF, DKIM & DMARC records for email deliverability and security issues.
Use a sender identity Gmail can trust
Gmail evaluates whether the visible sender identity is credible. Keep the From display name and address consistent with the organization sending the message. Third-party tracking domains are not automatically unsafe, but unrelated branding and deceptive redirects deserve investigation. Do not use 'Re:' or 'Fwd:' in the subject unless the message is an actual reply or forward.
Risky setup
- From domain: Uses a brand domain, but SPF passes for an unrelated platform domain and no DKIM signature satisfies DMARC alignment.
- DKIM domain: Signs only with an unrelated platform domain, with no SPF result that satisfies DMARC alignment.
- Links: Use unrelated short links or tracking domains.
Cleaner setup
- From domain: Has DMARC domain alignment with a passing SPF or DKIM result.
- DKIM domain: Uses a d= signing domain that meets the From domain's DMARC alignment requirements.
- Links: Use owned domains, stable redirects, and expected brand context.
For separate mail streams, consider authenticated subdomains. For example, marketing.example.com can handle campaigns while billing.example.com handles receipts. Each sending subdomain needs correctly authenticated sources. Subdomains help organize sending but do not guarantee separate reputation or exemption from Gmail's bulk-sender rules. An applicable parent DMARC policy can cover subdomains, so publish a separate subdomain record when it needs different policy or reporting.
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SPF | Envelope sender and sending IP | SPF pass with domain alignment when used for DMARC |
DKIM | Signature and signing domain | Valid signature with aligned domain |
DMARC | Alignment, policy, and reports | Passes through aligned SPF or DKIM |
Return-Path | Envelope sender domain used by SPF | Meets From domain alignment if relying on SPF for DMARC |
Identity checks that matter before sending
If the setup has multiple sending tools, use Suped's domain health check to inspect public DNS settings before changing content. Confirm the affected message's results in Gmail as well, because DNS checks alone do not prove how that message was authenticated.
Check links and landing pages
After authentication, inspect every URL in the message. Gmail can warn when links point to compromised hosts, suspicious redirects, deceptive login pages, or domains that do not fit the sender. This includes visible links, hidden tracking links, image URLs, unsubscribe links, and redirects added by the email platform. Google describes its dangerous-link warnings in the Gmail security overview.
A common failure pattern is a legitimate sender linking to a landing page that asks for credentials or payment details without enough context. Another is a message that says it comes from one brand but sends the recipient through a chain of tracking, link wrapping, and redirect domains before the final page. Gmail's warning is often about the path, not only the final page.
Email link checks for Gmail security warnings: visible URL, tracking redirect, final domain, and page request.
- Owned domains: Use domains your recipients already associate with your organization.
- Redirect chains: Keep redirects short, predictable, and HTTPS-only.
- Login pages: Avoid sending users directly to credential forms without clear account context.
- Compromise checks: Inspect linked pages for injected scripts, unexpected redirects, malware warnings, and expired certificates.
If Gmail warns on a message that otherwise authenticates correctly, simplify the email and test again. Remove tracking links, shorten the redirect path, replace third-party short URLs with your own domain, and send the same message to a different Gmail inbox. If the warning disappears, add pieces back one at a time.
Do not try to hide risky links behind friendly anchor text. Gmail and users both compare the visible promise with the technical destination. A mismatch can make a legitimate campaign look unsafe.
Fix encryption and attachment warnings
A red open padlock means a message is unencrypted, as explained in Google's email encryption guidance. For outgoing mail, have your provider or mail administrator enable SMTP TLS and confirm the delivered Gmail copy reports standard encryption. HTTPS on a landing page does not encrypt email transport, and SPF, DKIM, and DMARC do not replace TLS.
Attachment warnings need a file-specific check. Gmail blocks certain executable files even inside archives, as described in Google's blocked-file guidance. It also warns when it cannot scan encrypted attachments; that warning alone does not establish that the file is infected.
- If malware is detected, stop sending the file and investigate its source before creating a clean replacement.
- If Gmail cannot scan an encrypted document, use an approved secure sharing workflow. Keep any encryption required to protect sensitive files.
- If the file type is blocked, remove the attachment or provide a permitted format. Renaming the file or putting it inside a ZIP archive does not resolve the underlying restriction.
- If Gmail says its virus scanner is temporarily unavailable, wait and retry. A temporary scan failure is different from a confirmed infection.
Gmail's attachment scanning guidance distinguishes detected viruses from temporary scanner failures. Neither issue is fixed by changing a DMARC policy.
Test the message like a recipient
Compare tests with the affected production message. Sending from sender@example.com to the same address through an email platform is not, by itself, proof of a Gmail warning trigger. Use separate recipient accounts to check whether the result is specific to one mailbox, and compare authentication and message content before drawing a conclusion.
Send to personal Gmail, Google Workspace, and non-Gmail mailboxes. Test with a From address that is not the same as the recipient. For mail sent through an email platform, use a domain you control and authenticate, rather than placing an @gmail.com address in the From header. Compare headers and warnings across those inboxes.
Email tester
Send a real email to this address. Suped shows a results button when the test is ready.
?/43tests passed
A practical test starts with one message and one controlled change at a time. Use Suped's email tester to inspect the delivered test, then compare the same message in Gmail. On Gmail's desktop website, open the message, choose More next to Reply, and select Show original. Check Gmail's Authentication-Results, including spf=, dkim=, and dmarc=, plus the domains behind each result. The sender dropdown also shows 'Mailed by' and 'Signed by'.
Gmail 'Be careful with this message' security warning above an opened email.
- Baseline: Send a plain text version with no tracking and no links.
- Authenticate: Check SPF, DKIM, and DMARC in Show original. Confirm a passing SPF or DKIM result has the domain alignment required for DMARC.
- Add links: Add the final URL first, then add tracking only after the clean version passes.
- Change recipients: Compare separate Gmail accounts using the same sender and message, then investigate any result that differs by recipient.
Protect reputation and sending behavior
Gmail security warnings are not only about DNS. Sender reputation, spam complaint rates, sending patterns, list quality, and domain history matter. A new domain sending large campaigns immediately looks different from an established domain sending consistent mail to people who asked for it.
Investigate authentication failures and reputation signals separately. A bad DNS record or DKIM selector has a specific technical fix. Reputation reflects sending behavior over time, and authentication passing does not guarantee that a phishing or spam warning will disappear.
Sending risk signals to review
Qualitative troubleshooting categories, not measured thresholds or Gmail warning scores.
Low risk
Stable
Authenticated mail, expected volume, clean links, and low complaints.
Warning
Review
New sender, rising complaints, link changes, or uneven authentication.
High risk
Stop
Failed domain alignment, suspicious pages, sudden spikes, or poor list quality.
- Volume: Warm new domains and IPs gradually instead of jumping straight into large sends.
- Consent: Send to people who requested the mail, suppress invalid addresses, and stop mailing recipients who have withdrawn consent.
- Complaints: Keep Gmail's user-reported spam rate below 0.1% and prevent it from reaching 0.3% or higher. Pause campaigns that increase complaints.
- Blocklists: Check whether sending domains or IPs appear on a blocklist or blacklist before blaming content.
- Unsubscribe: Honor unsubscribe requests within 48 hours. For bulk marketing mail, a footer link alone does not replace RFC 8058 one-click unsubscribe headers.
If warnings appear after a sending spike, a list import, or a content change, pause the affected segment and compare recent sends with older clean sends. Google's bulk-sender FAQ recommends the complaint-rate targets above. Suped's blocklist monitoring tracks listed domains and IPs alongside authentication issues. A clean blocklist (blacklist) result does not prove Gmail considers the sender safe.
Issue steps to fix dialog showing the issue overview, tailored fix steps, and verification action
Gmail security warning checklist
When a Gmail warning appears, do not start by rewriting the whole campaign. Preserve the original message, gather the headers, and work down a checklist. That keeps the investigation factual and prevents random changes that hide the real cause.
Match the checklist to the warning text. For a sender-verification warning, verify authentication and From-domain alignment first. For a red padlock or attachment warning, check TLS or the named file before changing campaign content.
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1 | Auth fail | Fix SPF, DKIM, DMARC |
2 | Misalignment | Use aligned domains |
3 | Bad link | Clean redirect path |
4 | Test artifact | Compare recipients and delivered headers |
5 | Reputation | Stabilize volume and list |
6 | No transport encryption | Enable SMTP TLS and verify in Gmail |
7 | Unsafe or unscannable attachment | Investigate the file and use a safe delivery format |
Troubleshooting sequence for Gmail warnings
Use Suped's DMARC reports to identify the source and authentication result, then verify the affected message in Gmail. DMARC aggregate reports do not show Gmail's banner text, attachment scan result, or the safety of a landing page.
Gmail message checks to inspecttext
Authentication-Results: use the results added by Gmail SPF: spf=pass; inspect smtp.mailfrom DKIM: dkim=pass; inspect header.d and DKIM-Signature d= DMARC: dmarc=pass; inspect header.from Return-Path: envelope sender domain used by SPF From: visible sender domain checked by DMARC ARC: inspect authentication history after forwarding TLS: confirm encryption in Gmail message details
If warnings persist, preserve a fresh example with the full headers and exact warning text, then ask the sending provider to investigate. For Google Workspace recipients, have the recipient's administrator check whether an organization-specific policy explains the banner. Retest after a specific fix; there is no guaranteed waiting period that removes a warning.
