Why is Gmail showing 'This message seems dangerous' warning?
Michael Ko
Co-founder & CEO, Suped
Published 24 Jul 2025
Updated 15 Aug 2025
6 min read
Receiving an email in Gmail with the stark warning, "This message seems dangerous. Many people marked similar messages as phishing scams, so this might contain unsafe content. Avoid clicking links, downloading attachments, or replying with personal information," can be concerning for any sender. It implies a serious issue with your email's legitimacy or your domain's reputation.
This warning isn't just a minor inconvenience, it's a significant barrier to your message reaching its intended audience and can severely impact your email deliverability. When Gmail flags an email as dangerous, it's a strong signal that something is amiss, often related to security, authentication, or sender reputation.
Understanding Gmail's security warnings
Gmail employs sophisticated algorithms and user feedback to identify potentially malicious emails. These systems analyze various factors, including sender reputation, content, links, and authentication records, to protect users from phishing, malware, and spam. The 'This message seems dangerous' warning is a prominent visual alert designed to deter recipients from interacting with potentially harmful content.
The core purpose behind these warnings is user safety. If Gmail's systems detect anything that resembles a phishing attempt, a scam, or a message from a compromised sender, it will display this red banner. This proactive approach helps prevent account takeovers, data breaches, and the spread of malicious software.
Understanding these warnings is crucial for maintaining good email deliverability. A persistent 'dangerous message' alert can lead to your emails being consistently sent to spam, or even blocked entirely. It's a clear indicator that Gmaillacks trust in your sending practices.
Common triggers for the 'Dangerous' warning
The 'This message seems dangerous' warning typically stems from several key factors that raise red flags with Gmail's security protocols. One of the most common reasons is a poor or compromised sender reputation. If your domain or IP address has been associated with spam, phishing, or other malicious activities in the past, Gmail will view your emails with suspicion. This is often linked to being present on an email blocklist (or blacklist).
Another significant trigger is the presence of suspicious links or content within the email itself. Gmail scrutinizes URLs for signs of malicious intent, such as redirecting to known phishing sites or containing deceptive characters. Even legitimate links can be flagged if the domain they point to has a poor reputation or is currently compromised. You can check the safety of a site using Google's Safe Browsing site checker.
Lack of proper email authentication is also a major contributor. If your emails fail SPF, DKIM, or DMARC checks, Gmail can't verify that the message truly originated from your domain, making it suspicious. This vulnerability is often exploited in spoofing and phishing attacks, leading Gmail to err on the side of caution.
Technical deep dive into email authentication
Email authentication protocols are the bedrock of trust in email communication. SPF, DKIM, and DMARC work together to verify that an email sender is legitimate and authorized to send emails on behalf of a domain. When these are misconfigured or missing, it creates an easy target for malicious actors to impersonate your brand.
Problem: authentication issues
Without proper SPF, DKIM, and DMARC records, Gmail cannot reliably confirm your email's origin, making it prone to 'dangerous message' warnings or direct spam folder placement. This undermines recipient trust and your sender reputation.
SPF Failures: Allowing unauthorized servers to send mail on your domain's behalf.
DKIM Failures: Emails tampered with in transit or incorrect cryptographic signatures.
DMARC Absence: No defined policy for recipients on how to handle unauthenticated mail.
A common cause for these warnings is when Gmail cannot verify the sender of the email. This can happen if your domain's DNS records are incorrectly configured, or if you're sending emails from a domain that isn't properly authenticated. Here's an example of a simple SPF record that authorizes your mail server:
Example SPF recordTXT
v=spf1 ip4:192.0.2.1 include:spf.example.com ~all
Remediation steps and long-term prevention
When faced with the 'This message seems dangerous' warning, the first step is to identify the root cause. Start by checking your email authentication records for any errors or misconfigurations. Then, inspect the content of your emails, especially any links or attachments. Use a tool like Google Postmaster Tools to gain insights into your sender reputation, spam rates, and domain health.
If your domain or IP address has landed on a public blocklist (or blacklist), you'll need to submit a delisting request. Each blocklist operator has its own process, so it's important to follow their specific instructions. However, remember that delisting is often a temporary solution if the underlying issues, such as poor sending practices or a compromised system, are not addressed. Regularly monitoring blocklists is key to proactive management.
Implement DMARC: Set up a DMARC policy to gain visibility into your email ecosystem and prevent unauthorized use of your domain.
Maintain high sender reputation: Send relevant content, avoid sending to inactive addresses, and manage bounces effectively.
Ensure secure links: Verify that all links in your emails use HTTPS and are not associated with any reported phishing or malware sites.
Regularly audit email content: Look for phrases or patterns that could be misinterpreted as phishing attempts.
Ensure all links, including those in images and ESP default links, use HTTPS to avoid security warnings.
Regularly monitor your domain's reputation using tools like Google Postmaster Tools.
Implement and enforce DMARC policies to prevent spoofing and improve trust.
Verify that your email content does not inadvertently trigger spam filters, particularly for sensitive topics.
Common pitfalls
Using insecure links (HTTP instead of HTTPS) for images or tracking URLs.
Having a compromised website or hosting malicious content on linked domains.
Not configuring SPF, DKIM, and DMARC records correctly or at all.
Sudden changes in email volume or content that can appear suspicious to ISPs.
Expert tips
Actively use Google Postmaster Tools to track your domain's health and identify issues early.
Scan all links within your emails using security tools to detect any hidden malicious URLs.
If using an ESP, ensure their sending practices align with your deliverability goals.
Conduct regular email deliverability tests to identify potential problems before they impact recipients.
Marketer view
A marketer from Email Geeks says that the 'This message seems dangerous' warning could be an issue with either the domain used in the links or the 'from' domain, or even a compromised site hosting something suspicious.
March 26, 2020 - Email Geeks
Marketer view
A marketer from Email Geeks indicates that it's crucial to identify the specific dangerous URL if Google's Safe Browsing report only indicates harmful software but not the exact link.
March 27, 2020 - Email Geeks
Ensuring email trust and deliverability
The 'This message seems dangerous' warning from Gmail is a critical signal that your email deliverability and sender reputation are at risk. It's a call to action to investigate and resolve underlying issues related to email authentication, link security, and content quality.
By diligently implementing email authentication protocols like SPF, DKIM, and DMARC, maintaining a healthy sender reputation, and ensuring the security of all links, you can build trust with Gmail and significantly improve your inbox placement rates.
Gmail with the stark warning, "This message seems dangerous. Many people marked similar messages as phishing scams, so this might contain unsafe content. Avoid clicking links, downloading attachments, or replying with personal information," can be concerning for any sender. It implies a serious issue with your email's legitimacy or your domain's reputation.
