Why did Gmail mark an internal email as potentially dangerous?

Key findings

• Algorithmic detection: Gmail uses sophisticated machine learning models to identify suspicious emails. These models analyze various email attributes, not just sender reputation or authentication, to determine if a message poses a risk. The warning is a proactive alert, not a spam classification.
• Content analysis: Even without external links, specific keywords (like those related to 'marketing' or 'CAN-SPAM'), a 'spammy' subject line, or even the presence of certain attachments (such as a company logo within an email signature if not handled optimally) can contribute to the email being flagged. This is why legitimate emails can sometimes trigger inconsistent suspicious link warnings.
• Internal phishing simulations: If an organization regularly sends internal phishing test emails, it might inadvertently train Gmail's algorithms to be more sensitive to certain internal email patterns, increasing the likelihood of false positives. Users reporting emails as phishing or spam (even for training) can influence Gmail's learning process.
• No single cause: It is often a combination of factors, rather than a single element like a low sender reputation or explicit trigger words, that leads to an email being marked as potentially dangerous.

Key considerations

• Review email content: Even for internal communications, avoid overly aggressive, promotional, or sensational subject lines. Review the body for phrases that might be common in phishing or spam emails. Be mindful of attachments, even if they are benign images.
• Check audit logs: Your IT team or Google Workspace administrator should be able to access mail audit logs to gain more insight into why the email was flagged. This can provide specific reasons or indicators that triggered the warning.
• User interaction: When users click Looks safe on a flagged email, it helps train Gmail's model, potentially reducing similar future flags for that sender or content pattern.
• DMARC, SPF, and DKIM alignment: Ensure your domain's email authentication records (SPF, DKIM, DMARC) are correctly configured, even for internal mail. While less common for internal flags, misconfigurations can sometimes contribute to general distrust, including internal warnings. You can learn more in a simple guide to DMARC, SPF, and DKIM.

Key opinions

• Content matters: Even for internal emails, the subject line and body content (especially if it mentions terms like 'marketing' or 'CAN-SPAM') can trigger warnings, despite the common belief that trigger words aren't a factor. This explains why google may flag your content as malicious.
• Beyond spam filters: If an email goes to the inbox but still shows a warning, it's not a direct spam filter issue (where the email is sent to the spam folder or blocked). Instead, it's a safety flag indicating Google's concern about potentially dangerous content.
• Attachments can be a factor: Even seemingly innocuous attachments, like a company logo in an email signature, could contribute to an email being flagged, especially if combined with other suspicious elements.
• User behavior impact: User actions, such as reporting an internal email as spam (even in jest or during training), can influence Gmail's perception of future emails from that sender or domain. Manually marking a message as not spam helps train Gmail to improve its filtering.

Key considerations

• Be cautious with 'spammy' content: Even for internal communications, avoid subject lines or content designed to be overly attention-grabbing if they resemble common spam tactics. This applies to internal emails with shortened links or shared sender names.
• Review email signatures: Ensure elements within signatures, especially images or complex HTML, are optimized and don't inadvertently trigger warnings. Consider embedding logos rather than attaching them where possible.
• Educate colleagues: Inform internal users about Gmail's warning mechanisms and the potential impact of their email content choices, even within the corporate network. Emphasize that whitelisting all internal addresses is dangerous.
• Monitor delivery internally: While internal emails might not appear in public deliverability tools, paying attention to internal warnings can offer clues about content that might trigger issues for external recipients.

Key opinions

• Machine learning driven: Gmail's warnings are driven by complex machine learning models that can produce maybe results, adding alerts when an email might be dangerous. User feedback (e.g., marking as safe) helps train these models.
• Content similarity: While literal 'spam trigger words' might not be the sole cause, if the email's language or structure resembles other content Gmail flags as spam or suspicious, it can still trigger an alert. This can be problematic for emails triggering phishing warnings.
• Diagnostic limitations: It's often impossible to point to one specific element (like a URL or a single word) as the exact cause, due to the complex nature of the ML models.
• Internal audit logs: For Google Workspace users, checking the mail audit log can provide more specific information on why an internal email was flagged, potentially indicating a false positive or something actionable. Learn more about email protection features.

Key considerations

• Header review: Although the email went to the inbox, examining email headers for any failed authentication (SPF, DKIM, DMARC) or unusual routing could provide clues, even if they don't directly cause the this message seems dangerouswarning.
• Internal training sensitivity: Be aware that internal phishing training exercises, while beneficial for security, might increase Gmail's vigilance towards similar-looking internal emails.
• No quick fix: Because ML models are complex, there isn't usually a single 'smoking gun' to identify and fix. It's an ongoing process of monitoring and content adjustment.
• Domain reputation and internal mail: While external sender reputation is critical for marketing emails, internal emails can still be influenced by how Gmail perceives the overall trust of your domain, including factors that might lead to emails from unindexed domains being marked as dangerous.

Key findings

• Phishing and malware detection: Gmail's warnings are fundamentally designed to alert users about potentially harmful content, restricting access or flagging emails to protect against online security threats. This is a primary function for preventing phishing warnings.
• AI and behavioral analysis: Modern email security systems utilize AI to analyze email content, sender behavior, and domain reputation. Even subtle anomalies can trigger alerts, as seen with Gmail's AI security vulnerabilities where legitimate emails might be flagged.
• Authentication standards: Failure to follow email authentication standards (like SPF, DKIM, DMARC) can lead to emails being rejected or tagged as spam, even from internal sources. While not always the direct cause of a dangerous warning, proper authentication is foundational for trust, as highlighted by Microsoft 365 admins being warned about new Google anti-spam rules.
• Contextual analysis: Google's systems analyze the entire email context—sender, content, links, attachments, and historical patterns—to determine potential risk. This holistic approach means that a single, seemingly harmless element can contribute to a warning if it fits a broader dangerous pattern.

Key considerations

• Internal email guidelines: Organizations should establish clear guidelines for internal email content, particularly for sensitive or attention-grabbing messages, to avoid inadvertently triggering security warnings. This can include guidance on formatting, attachments, and subject lines.
• Review email authentication: Regularly check your domain's SPF, DKIM, and DMARC records to ensure they are correctly configured and aligned, even for internal email flow within Google Workspace. This helps maintain the domain's overall trust and can prevent issues like common DMARC issues.
• Stay informed on security updates: Keep abreast of security updates and best practices from Google and other email providers. New features, such as enhanced DKIM signature checks, are continuously rolled out to combat evolving threats.
• Feedback mechanisms: Encourage users to report false positives when an internal email is flagged. This user feedback is crucial for Google's machine learning algorithms to learn and refine their detection capabilities over time.