How do I troubleshoot Gmail phishing email warnings?
Michael Ko
Co-founder & CEO, Suped
Published 17 Jun 2025
Updated 18 Aug 2025
8 min read
Receiving a phishing email warning in Gmail can be unsettling, especially when you believe the message is legitimate. These warnings, often appearing as banners like "Be careful with this message" or "This message seems dangerous", indicate that Google's robust security systems have flagged the email as potentially malicious. While Gmail is excellent at protecting users, sometimes legitimate messages can be caught in these filters, causing deliverability headaches.
Troubleshooting these warnings requires a methodical approach, looking beyond just the basics. It is essential to understand that an email passing SPF, DKIM, and DMARC does not guarantee it will bypass these warnings, as other factors related to content, sender reputation, and user behavior play a significant role. My aim here is to guide you through the common causes and solutions for these frustrating Gmail phishing warnings.
Why Gmail flags emails as phishing
Gmail employs sophisticated algorithms to detect phishing attempts, which go beyond standard email authentication protocols. While strong authentication is a prerequisite for good deliverability, these warnings often stem from a deeper analysis of the email's content, the sender's historical reputation, and even the behavior of the recipients. This means a message can pass all technical checks and still be flagged if it exhibits characteristics common to phishing scams.
One primary reason for these warnings is suspicious content within the email. This includes urgent language, requests for sensitive information, unusual links (especially those that redirect), or even generic greetings. Google's systems are designed to identify patterns that suggest an attempt to trick users. For instance, an email asking you to "verify your account immediately" might trigger a warning, even if sent from a legitimate domain, if the phrasing is overly aggressive or resembles known phishing tactics. To understand why emails can get these warnings, even with no links, review our guide why emails get phishing warnings even with no links.
Sender reputation is another critical factor. If your domain or IP address has a history of sending spam or malicious content, or if there's a sudden spike in email volume or a change in sending patterns, Gmail might view this as suspicious. Even if your current email is clean, past issues can lead to warnings. Google aims to protect its users, and a sender's poor reputation is a strong signal that an email might be risky. This applies even if you have proper DMARC, SPF, and DKIM setup, as these warnings are often reputation-based.
Authentication issues
Missing records: SPF, DKIM, or DMARC records are not correctly set up or are missing entirely. This makes it impossible for Gmail to verify the sender's legitimacy.
Misconfigured records: Errors in your DNS records, such as incorrect SPF syntax or an invalid DKIM key, can cause authentication failures.
DMARC policy: A DMARC policy set to 'reject' (p=reject) with authentication failures can lead to messages being blocked outright or heavily scrutinized.
Phishy language: Urgency, threats, requests for personal data, or unusual financial requests within the email body.
Low sender reputation: A history of high spam complaints, sending to inactive addresses, or being listed on a blocklist (or blacklist) can degrade your sender reputation.
Verify your email authentication (SPF, DKIM, DMARC)
The first step in troubleshooting is to ensure your email authentication is impeccable. This means correctly configuring SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance). These records verify that your emails are indeed coming from your domain and haven't been tampered with. Even if your emails pass DMARC, warnings can still appear, which we discuss in depth in our guide why Gmail shows a warning message despite passing DMARC.
For SPF, make sure your record includes all authorized sending IP addresses and third-party senders. An example SPF record might look like this:
DKIM involves adding a cryptographic signature to your outgoing emails, which Gmail uses to verify that the message hasn't been altered in transit. Ensure your DKIM keys are correctly published in your DNS. DMARC builds on SPF and DKIM by allowing you to specify how recipient email servers should handle emails that fail authentication. I always recommend starting with a DMARC policy of p=none to gather reports before moving to quarantine or reject policies. You can generate a free DMARC record using our free DMARC record generator tool.
Important for authentication
Even with perfect SPF, DKIM, and DMARC alignment, Gmail may still flag emails if other suspicious indicators are present. Authentication is necessary, but not always sufficient, to entirely prevent phishing warnings. Always monitor your domain reputation in Google Postmaster Tools.
Review email content and sender reputation
Beyond technical authentication, the content and overall sender reputation are key. Gmail's filters analyze the language, links, and attachments within your emails. Using highly suspicious phrases, even innocuously, can trigger a warning. For example, language that creates a false sense of urgency or solicits sensitive information, like bank details or passwords, is a major red flag. If you are experiencing Gmail phishing warnings, consider a content audit.
The links in your emails are also heavily scrutinized. If your emails contain links to domains that are frequently associated with malware or phishing, or if the display URL doesn't match the actual destination URL, Gmail will likely flag it. Using URL shorteners extensively can also be problematic, as they obscure the final destination. Ensure all links point to trusted, legitimate domains that are consistent with your brand identity. You can refer to this FTC guide on recognizing and avoiding phishing scams for more insights into what content is typically flagged.
Your sender reputation (the trustworthiness of your domain and IP) significantly impacts how Gmail treats your emails. A high spam complaint rate, bounces, or being listed on a public blacklist (or blocklist) can severely damage your reputation. Even if the content is benign, a poor reputation will cause Gmail to err on the side of caution. We also have a dedicated tool for blocklist monitoring to help you stay on top of this. Regularly cleaning your email list to remove inactive or invalid addresses, monitoring engagement rates, and ensuring recipients genuinely want your emails are crucial steps in building and maintaining a strong sender reputation.
Content element
What to avoid
Why it triggers warnings
Links
URLs with suspicious domains, mismatch between display and actual URL, excessive URL shorteners.
Indicates potential malicious redirection or hidden destinations, common in phishing attacks.
Language
Urgent calls to action, threats (e.g., account suspension), requests for personal/financial data, generic greetings.
Mimics common social engineering tactics used to manipulate recipients into revealing information.
Attachments
Unexpected files, executables, or compressed files, especially from unknown senders.
Common method for malware distribution; Gmail scans for malicious payloads.
Advanced troubleshooting and prevention
If you've checked authentication and content, and still face warnings, it might be time for more advanced troubleshooting. Regularly monitoring your domain's health through Google Postmaster Tools is invaluable. This free tool provides insights into your sending reputation, spam rates, and DMARC failures, helping you pinpoint issues before they escalate. It's a fundamental part of maintaining good standing with Google. Learn how to improve your domain reputation using this resource.
User engagement also plays a subtle but significant role. If recipients frequently mark your emails as spam, or if open and click-through rates are consistently low, it signals to Gmail that your emails might be unwanted or suspicious. Encouraging positive engagement through relevant content, clear calls to action, and accessible unsubscribe options can improve your sender score and reduce the likelihood of warnings. Conversely, a lack of engagement can indicate that your emails are not valuable, contributing to reputation issues.
Finally, ensure that your email sending infrastructure and practices align with Google's bulk sender guidelines. This includes sending from a dedicated IP address (if volume is high enough), maintaining a consistent sending volume, and adhering to permission-based sending. For internal emails with shortened links or shared sender names, specific precautions are often needed to prevent phishing warnings. Our article, how to prevent Gmail phishing warnings for internal emails, offers further guidance. By taking a holistic approach, addressing both technical and content-related factors, you can significantly reduce Gmail phishing warnings.
Views from the trenches
Best practices
Maintain clean email lists to prevent sending to inactive or spam trap addresses, which hurt reputation.
Consistently monitor your Google Postmaster Tools dashboard for any alerts on your domain's reputation.
Use clear, transparent language in your emails and avoid any terms that could be misinterpreted as phishing.
Always use full, verifiable links to trusted domains, avoiding URL shorteners where possible.
Ensure your email authentication records (SPF, DKIM, DMARC) are correctly configured and monitored.
Common pitfalls
Ignoring Google Postmaster Tools warnings, leading to unaddressed deliverability issues.
Using generic email templates that contain phrasing commonly associated with phishing scams.
Sending emails with inconsistent volumes or from new, un-warmed-up IP addresses.
Not implementing or incorrectly configuring DMARC, leaving your domain vulnerable to spoofing.
Including unexpected attachments or obscure file types in your emails.
Expert tips
Consider sending test emails to a variety of Gmail accounts to observe how they are rendered and if any warnings appear.
Segment your audience and tailor content to improve engagement, reducing the likelihood of spam complaints.
For transactional emails, prioritize clarity and directness over promotional language to build trust.
Regularly check if your domain or IP is listed on any public blacklists using a blocklist checker.
Implement a strong DMARC policy (p=quarantine or p=reject) once confident in your authentication alignment.
Marketer view
Marketer from Email Geeks says that even with perfect SPF, DKIM, and DMARC authentication, emails can still be flagged as possible phishing if the content or sender behavior triggers Gmail's content detectors. This means authentication alone is not a complete solution for these warnings.
2020-04-07 - Email Geeks
Expert view
Expert from Email Geeks says that the phishing warning is often triggered by Gmail's content detector, which analyzes the phrasing, structure, variables in links, and the landing page associated with the email. It is not necessarily an authentication issue.
2020-04-07 - Email Geeks
Key takeaways
Troubleshooting Gmail phishing email warnings requires a comprehensive approach, combining technical diligence with careful attention to content and sender reputation. While robust SPF, DKIM, and DMARC configurations are foundational, they are just one piece of the puzzle. Google's advanced filters continuously analyze email content, link destinations, and your historical sending behavior to protect its users.
By actively monitoring your domain's health through tools like Google Postmaster Tools, ensuring your email content avoids suspicious phrasing, using legitimate and transparent links, and maintaining a high sender reputation through good list hygiene and engagement, you can significantly reduce the likelihood of your legitimate emails being flagged. Staying proactive and adapting your sending practices to evolving security standards is key to successful email deliverability.
