Summary
Gmail's 'This message seems dangerous' warning is triggered by several factors, primarily related to suspected phishing or malware, sender reputation, and email authentication. Suspicious links, spammy content, and unusual sending patterns are red flags. Authentication failures (SPF, DKIM, DMARC) are a major cause, as are blacklisted domains or IPs, compromised websites, and insecure links. Poor email practices like high bounce rates and spam complaints contribute to low sender reputation. Additionally, link masking, inconsistent sending volumes, and even well-intentioned marketing emails triggering spam filters can result in the warning.
Key findings
- Phishing/Malware Suspicions: Gmail identifies and flags messages containing content that seems like phishing attempts or malware distribution.
- Authentication Failures: Improper or missing SPF, DKIM, and DMARC records result in authentication failures and trigger the warning.
- Low Sender Reputation: Poor sending practices (high bounce rates, spam complaints) negatively impact sender reputation, increasing the risk of warnings.
- Compromised Websites/Blacklisting: A compromised website or blacklisted domain/IP will trigger the warning.
- Insecure Links and Practices: Insecure (HTTP) links, SSL certificate issues, and the use of link masking increase the likelihood of the warning.
Key considerations
- Implement Email Authentication: Properly configure SPF, DKIM, and DMARC records to verify your sender identity and prevent spoofing.
- Maintain Sender Reputation: Practice good email hygiene: clean your email lists, minimize bounce rates and spam complaints, and warm up IP addresses properly.
- Review Email Content: Carefully review your email content, avoiding spammy keywords, deceptive language, and ensure it's not triggering spam filters inadvertently.
- Secure Your Website and Links: Ensure your website is secure, scan for malware regularly, and always use secure (HTTPS) links.
- Avoid Link Masking: Refrain from using link masking or redirection services that can negatively impact your reputation.
- Monitor Sending Volume: Maintain consistent sending volumes to avoid triggering spam filters.
- Use Google Tools: Leverage tools like Google's Safe Browsing and Webmaster Tools to identify and resolve security issues.
What email marketers say
9 marketer opinions
Gmail's 'This message seems dangerous' warning appears primarily due to suspected phishing, malware, or poor sender reputation. Issues include suspicious links, spammy content, authentication failures (SPF, DKIM, DMARC), blacklisted domains or IPs, insecure links/SSL certificates, and poor email practices such as high bounce rates or spam complaints. Consistent sending volumes, avoiding URL shorteners, and maintaining a clean email list are also important factors.
Key opinions
- Phishing/Malware Suspicions: Gmail flags messages containing links or content it believes may be used for phishing or distributing malware.
- Authentication Failures: Incorrect or missing SPF, DKIM, and DMARC records are a major cause of the warning.
- Sender Reputation: Low sender reputation due to poor email practices (high bounce rates, spam complaints) significantly increases the risk of the warning.
- Blacklisting: If your domain or sending IP is blacklisted, Gmail is likely to flag your messages.
- Insecure Content: Insecure links (HTTP instead of HTTPS) and SSL certificate issues can also trigger the warning.
Key considerations
- Email Authentication: Ensure SPF, DKIM, and DMARC are correctly configured to verify your identity as a legitimate sender.
- Sender Reputation Management: Maintain a good sender reputation by practicing good email hygiene, such as cleaning your email list, avoiding spam traps, and minimizing bounce rates and spam complaints.
- Content Review: Carefully review your email content for any elements that might be perceived as suspicious, such as spammy keywords or masked links.
- Secure Links: Always use secure links (HTTPS) for all URLs in your email, including images and unsubscribe links.
- Sending Practices: Maintain consistent sending volumes and avoid sudden spikes in email frequency.
- Monitor Feedback Loops: Actively monitor feedback loops to identify and address issues causing spam complaints.
Marketer view
Email marketer from SendPulse Blog responds that the warning could mean that the email failed authentication checks, the sender's IP is blacklisted, or the email content resembles phishing attempts.
15 May 2025 - SendPulse Blog
Marketer view
Email marketer from Google Support explains that the 'This message seems dangerous' warning appears when Gmail suspects phishing or malware. Users should avoid clicking links or providing personal information.
28 Dec 2021 - Google Support
What the experts say
5 expert opinions
Gmail's 'This message seems dangerous' warning can stem from a compromised website hosting malicious content, the use of link masking or redirection services which negatively impacts reputation due to association with malicious activity, or even well-intentioned marketing emails triggering spam filters. Google's Safe Browsing tool and Webmaster Tools are suggested for identifying malicious links. It's essential to maintain a reputable sending infrastructure and avoid deceptive content.
Key opinions
- Compromised Website: A compromised website hosting malicious content can trigger the Gmail warning.
- Link Masking/Redirection: Using link masking or redirection services negatively impacts sender reputation and increases the likelihood of Gmail flagging the message.
- Spam Filters Triggered: Even legitimate marketing emails can inadvertently trigger spam filters, leading to the warning.
Key considerations
- Website Security: Regularly scan your website for malware and vulnerabilities to ensure it's not compromised.
- Avoid Link Masking: Refrain from using link masking or redirection services to maintain a transparent and trustworthy link structure.
- Content Review: Carefully review email content to ensure it isn't deceptive or likely to trigger spam filters.
- Sending Infrastructure: Ensure your sending infrastructure is reputable and properly configured to avoid being flagged as spam.
- Use Google Tools: Utilize Google's Safe Browsing tool and Webmaster Tools to identify and resolve any security issues related to your website and email sending practices.
Expert view
Expert from Word to the Wise, that even well-intentioned marketing emails can trigger spam filters and warnings, which could potentially cause a "This message seems dangerous" warning. Ensuring content isn't considered deceptive and uses a reputable sending infrastructure are key to avoiding such issues.
22 Feb 2024 - Word to the Wise
Expert view
Expert from Email Geeks recommends checking Google Webmaster Tools for more data on malicious links.
6 Jan 2023 - Email Geeks
What the documentation says
4 technical articles
Gmail's 'This message seems dangerous' warning is frequently caused by failures in email authentication. Properly configured SPF, DKIM, and DMARC records are essential for verifying sender identity and preventing email spoofing. When these authentication standards are missing or improperly implemented, Gmail flags the message as potentially dangerous.
Key findings
- Authentication Standards: Gmail relies on SPF, DKIM, and DMARC to authenticate senders.
- SPF Records: SPF records prevent email spoofing by specifying authorized mail servers.
- DKIM Signatures: DKIM uses digital signatures to authenticate the sender's identity.
- DMARC Policies: DMARC dictates how receivers should handle messages failing SPF and DKIM checks.
Key considerations
- Implement SPF: Ensure your SPF records are correctly configured to list all authorized mail servers for your domain.
- Implement DKIM: Enable DKIM signing for your emails to provide a digital signature that verifies the message's authenticity.
- Implement DMARC: Implement DMARC policies to instruct email receivers on how to handle messages that fail SPF and DKIM checks (e.g., quarantine or reject).
- Monitor Authentication: Regularly monitor your email authentication reports to identify and address any issues with SPF, DKIM, or DMARC.
Technical article
Documentation from RFC Editor describes that Sender Policy Framework (SPF) records prevent email spoofing by specifying which mail servers are authorized to send email on behalf of a domain. Misconfigured or missing SPF records can trigger warnings.
28 Oct 2021 - RFC 4408
Technical article
Documentation from DMARC.org outlines that Domain-based Message Authentication, Reporting & Conformance (DMARC) helps email receivers handle messages that fail SPF and DKIM checks, providing a policy for handling such messages (e.g., reject, quarantine). Missing or improperly configured DMARC records can lead to warnings.
23 Oct 2022 - DMARC.org
How can I avoid Gmail security warnings on emails?
How do I troubleshoot Gmail phishing email warnings?
Why are emails from a new .uk domain going to spam folders?
Why are my authenticated emails to Gmail soft bouncing with a DKIM and SPF fail error?
Why did Gmail mark an internal email as potentially dangerous?
Why is Gmail rejecting unauthenticated email from gmail.com due to DMARC policy when sending via Sendgrid?
