Why does Gsuite show an anti-phishing warning when sending emails?
Matthew Whittaker
Co-founder & CTO, Suped
Published 14 Aug 2025
Updated 18 Aug 2025
9 min read
Sending emails from GSuite, now known as Google Workspace, can sometimes result in recipients seeing a prominent anti-phishing warning. It can be quite alarming to see a banner stating that your email might be dangerous or that GSuite couldn't verify the sender. These warnings are designed to protect users from malicious actors attempting to spoof legitimate entities or deliver harmful content. While frustrating for legitimate senders, understanding why these warnings appear is the first step toward preventing them.
Google employs sophisticated machine learning algorithms and a vast amount of data to identify and flag suspicious emails. Their goal is to safeguard users from phishing attacks, malware, and spam. Even if your emails are perfectly legitimate, certain characteristics can inadvertently trigger these protective measures. This often comes down to how your domain and email sending practices are perceived by Google’s advanced security systems. It's a balance between protecting recipients and ensuring legitimate mail flows smoothly.
The good news is that most of these issues are addressable. By optimizing your email setup and adhering to best practices, you can significantly reduce the likelihood of your emails triggering these anti-phishing warnings. It involves focusing on email authentication, maintaining a good sender reputation, and crafting your email content carefully.
Why Google Workspace shows warnings
Google's security measures are comprehensive, constantly evolving, and designed to preemptively identify potential threats. When you see a warning, it means that Google's phishing and malware protection systems have detected something unusual or potentially risky about your email. This isn't always a direct accusation of malicious intent, but rather a cautionary flag for the recipient.
A common type of warning involves messages that seem dangerous. This can occur if the sender's display name is similar to someone else in the recipient's organization but the actual email address doesn't match the organization's domain. It's Google's way of alerting users to potential employee spoofing, a common tactic used in targeted phishing attacks.
Another scenario where warnings pop up is when an email contains suspicious links, even if they point to seemingly legitimate HTTPS websites. Google's systems scrutinize links for unusual redirection patterns, hidden malware, or domains that are new or have a low reputation. This is why even well-intentioned emails can be flagged if they contain links to unindexed or untrusted domains.
Ultimately, these warnings are designed to empower the recipient with more information so they can make an informed decision about interacting with an email, rather than automatically blocking it. It shifts some of the responsibility to the user while providing a layer of protection.
Common triggers for warnings
Several factors can contribute to GSuite displaying anti-phishing warnings. Identifying the specific trigger for your emails is crucial for troubleshooting and implementing effective solutions. One of the primary culprits is inadequate email authentication.
Email authentication failures
Email authentication protocols like SPF, DKIM, and DMARC are fundamental for verifying the legitimacy of an email sender. If these are not correctly configured or fail validation checks, Gmail may be unable to verify the sender, leading to a warning. This is a clear signal that the email's origin cannot be trusted, opening the door for spoofing.
Sender reputation
A low or unestablished sender reputation can also trigger warnings, especially for emails from unindexed domains. If you're sending from a new domain or one that has previously been associated with spam or suspicious activity, Google's algorithms will be more cautious. This extends to IP address reputation as well, meaning if your sending IP is on a public blacklist or blocklist, you're more likely to see warnings.
Impersonation and spoofing
Even with proper authentication, GSuite's systems are vigilant against impersonation. If your sender's display name closely matches an internal employee's name but the email originates from an external domain, it can raise a flag. This is often referred to as employee spoofing. Additionally, if you're using shared sender names or shortened links, particularly in an internal context, it might also cause a warning. This highlights the complexity of identifying legitimate emails versus sophisticated phishing attempts that might even pass some authentication checks.
Suspicious content and links
The content of your email also plays a significant role. Unusual phrasing, common phishing keywords, or embedded links that Google deems suspicious can trigger warnings. This is true even if your email has no links at all. URL shorteners, unexpected attachments, or even images from untrusted sources can all contribute to an email being flagged as potentially harmful.
Technical solutions for warnings
Addressing GSuite anti-phishing warnings requires a multi-faceted approach, focusing on technical configurations and content best practices. Getting these foundations right is crucial for long-term email deliverability.
Proper email authentication
Implementing and correctly configuring SPF, DKIM, and DMARC is the most critical step. These records tell receiving mail servers that your emails are legitimate and authorized to send on behalf of your domain. A strong DMARC policy, moving beyond a 'p=none' policy, offers the best protection against spoofing and helps build trust with mailbox providers like Google. You can use a free DMARC record generator to get started.
Regularly check your DMARC reports to ensure that your emails are passing authentication checks and to identify any unauthorized sending of your domain. This proactive monitoring is key to maintaining a healthy sending reputation.
Building a strong sender reputation
Sender reputation is built over time through consistent, positive sending behavior. This includes maintaining a clean mailing list to minimize bounces, avoiding spam traps, and ensuring low complaint rates. If your domain is new, start with lower volumes and gradually increase to build trust with internet service providers (ISPs). Monitoring your domain reputation in Google Postmaster Tools is an excellent way to track your performance and identify potential issues early.
Content best practices
Review your email content for anything that might be perceived as suspicious. Avoid using overly aggressive sales language, excessive capitalization, or phrases commonly associated with spam or phishing. Be transparent about who you are and why you are emailing. If you include links, ensure they are clearly labeled and point to reputable, well-known domains. Shortened links should be used with caution, especially in internal communications, as they can obscure the true destination.
Advanced considerations and continuous monitoring
Beyond the initial setup, continuous monitoring and proactive management are essential to keep your emails out of the spam folder and avoid anti-phishing warnings. Email deliverability is an ongoing effort that requires vigilance and adaptation to evolving security standards.
Monitoring DMARC reports
DMARC reports provide invaluable insights into your email ecosystem. They show which emails are passing authentication, which are failing, and often provide reasons for failures. By regularly analyzing these reports using a DMARC monitoring solution, you can quickly identify and rectify issues that might lead to GSuite warnings, such as unauthorized senders attempting to spoof your domain.
Regularly check if your IP addresses or domain are listed on any email blacklists (or blocklists). Tools like a blocklist checker can help you stay on top of this. If you find your domain on an email blacklist, prompt action is required to request delisting. Performing periodic email deliverability tests also helps identify potential issues before they impact your recipient's inbox.
Key authentication records
Record Type
Purpose
Impact on warnings
SPF
Authorizes sending IP addresses for your domain.
Helps prevent spoofing of your domain.
DKIM
Verifies email content hasn't been tampered with.
Ensures message integrity and authenticity.
DMARC
Builds on SPF/DKIM, allows policy setting for failures.
Provides reporting on authentication status, crucial for managing warnings.
Views from the trenches
Here are some practical insights and observations from email deliverability professionals regarding GSuite anti-phishing warnings:
Best practices
Ensure SPF, DKIM, and DMARC records are correctly published and aligned for all sending sources.
Consistently monitor your domain and IP reputation using Google Postmaster Tools for any declines.
Educate users about what these warnings mean and how to identify truly suspicious emails.
Use clear, recognizable 'From' names and avoid internal-sounding names from external domains.
Gradually increase sending volume for new domains to build a positive reputation.
Common pitfalls
Forgetting to update SPF/DKIM records when changing email service providers.
Sending emails with display names that mimic internal employees from external domains.
Ignoring DMARC reports, missing critical insights into authentication failures or spoofing.
Using generic or untrusted URL shorteners that are often flagged by security filters.
Having an inconsistent sending pattern that can negatively impact sender reputation.
Expert tips
Implement a DMARC policy of p=quarantine or p=reject to actively protect your domain.
Regularly audit your email content for suspicious keywords or unusual formatting.
Consider a DMARC monitor to gain full visibility into your email authentication.
Check for blacklisting of your sending IPs and promptly request delisting if found.
Leverage Google's admin console settings to configure custom anti-phishing rules for your organization.
Marketer view
Marketer from Email Geeks says a phishing warning is common for new domains sending to GSuite accounts.
Dec 13, 2022 - Email Geeks
Marketer view
Marketer from Email Geeks says warnings are expected when emailing from outside the tenant, the sender name is similar to an internal user, and authentication isn't fully in place.
Dec 13, 2022 - Email Geeks
Ensuring email trust and security
GSuite's anti-phishing warnings, while sometimes a source of confusion, are a testament to Google's commitment to user security. They act as a critical line of defense against ever-evolving email threats like phishing and spoofing. By understanding the underlying reasons for these warnings, you can take concrete steps to improve your email deliverability and ensure your messages reach their intended recipients without unnecessary alerts.
The key takeaways are clear: robust email authentication (SPF, DKIM, DMARC) is non-negotiable, a positive sender reputation is paramount, and mindful content creation can prevent misidentification. Continuous monitoring and adaptation will keep your email program healthy and trusted by major mailbox providers, including Google.
