Why are my emails bouncing with REASON 552 5.7.0 in Gmail?
Matthew Whittaker
Co-founder & CTO, Suped
Published 7 May 2025
Updated 19 Aug 2025
8 min read
Receiving email bounce-backs with the error code "552 5.7.0 This message was blocked because its content presents a potential security issue" from Gmail can be a frustrating experience. It indicates that your email, despite reaching Gmail's servers, was rejected due to its content being flagged as potentially harmful or suspicious. This isn't a temporary issue, it's a hard bounce, meaning the email will not be delivered.
This specific error is a security measure implemented by Google to protect its users from phishing, malware, spam, and other malicious content. While it's designed to keep inboxes safe, it can be a significant hurdle for legitimate senders if their emails are inadvertently caught in this filter.
Understanding the root cause is crucial for resolving these bounces and ensuring your emails reach their intended recipients. I'll walk you through the common reasons for this error and provide actionable steps to diagnose and fix the problem.
Understanding the 552 5.7.0 error
The 552 5.7.0 error message from Gmail usually points to an issue with the email's content or attachments. Gmail's advanced filters scan messages for anything that might pose a threat, including suspicious links, unusual file types, or even patterns indicative of phishing attempts. When a message triggers these filters, it's immediately blocked to prevent potential harm to the recipient.
It’s important to distinguish this from other bounce codes, which might relate to recipient issues, server problems, or authentication failures. The 552 5.7.0 specifically targets the message's content as the source of the security concern. This means simply re-sending the same email will likely result in the same bounce.
In some cases, Gmail might also provide more specific details within the bounce message, such as "Your message may contain a virus" or "Banned file attachment", which can offer a direct clue. For a comprehensive list of reasons why Gmail might block messages, you can refer to their official support documentation.
Common causes of 552 5.7.0 bounces
One of the most frequent causes for a 552 5.7.0 bounce is suspicious or malicious links within your email. This includes links to domains known for hosting malware, phishing sites, or even legitimate domains that have been compromised. Gmail's filters are constantly updated to identify these threats.
Another factor is the use of link shorteners. While convenient, these can be abused by spammers to hide malicious URLs. If you use a generic link shortener that has a poor reputation, your emails might get caught by Gmail’s content filters. It's often safer to use full URLs or link shorteners provided by reputable email service providers.
A less obvious but significant cause, as identified by fellow email professionals, is the inclusion of email addresses directly in tracking or pixel links, particularly when formatted in specific ways. For example, if your tracking URL ends with an email address after a parameter like ?e=, Gmail may flag this as a security risk and bounce the email. It appears Google is tightening its stance on this practice, likely due to privacy and security concerns associated with exposing personal data in URLs.
While content is the primary driver, your sending IP's reputation can also play a role. If your IP address or sending domain has a poor reputation, even otherwise benign content might be scrutinized more heavily and trigger security alerts. Regularly monitoring your domain and IP reputation is critical for good deliverability.
Diagnosing and troubleshooting the bounce
When facing 552 5.7.0 bounces, the first step is always to examine the content of the bounced emails. Look for any common elements across the messages that are failing, especially links and attachments.
Inspect your links
Carefully review all URLs in your email. Look for:
Malware/Phishing: Are any domains known for malware or phishing? Even if they're not directly yours, if a CDN or third-party service you use is compromised, it could be the culprit.
Link Shorteners: Are you using services like bit.ly? While not always an issue, Gmail has been known to block certain generic ones.
Email Addresses in Links: Check your tracking pixels or embedded links for email addresses, especially if they are at the very end of the URL or preceded by parameters like ?e=.
Check your attachments
Gmail has a list of blocked file types that cannot be sent for security reasons. Ensure none of your attachments fall into this category. Also, attachments with suspicious file names or those packaged in multiple layers of compression (like nested zip files) can trigger security flags.
Utilize Google postmaster tools
If you're a bulk sender, Google Postmaster Tools (GPT) can be invaluable. While bounce data might have a slight delay, it provides insights into your domain and IP reputation, spam rate, and delivery errors, which can help pinpoint the problem. You can learn more about how to use these tools in our ultimate guide to Postmaster Tools.
Preventing future bounces
Once you've identified the problematic content or link, you'll need to adjust your email strategy. This often involves modifying your email templates or the way you track user interactions.
Content and link adjustments
If email addresses in tracking links are the cause, replace them with unique subscriber IDs or other non-personally identifiable information. Gmail's increasingly strict policies aim to enhance user privacy and security, and exposing email addresses in URLs contradicts this goal.
Review all links to ensure they lead to reputable, secure (HTTPS) domains. Avoid generic link shorteners. If you use third-party services for content delivery or tracking, verify their security practices and reputation. This is also important for why emails are suddenly rejected by Gmail more broadly.
Email authentication
While 552 5.7.0 is primarily a content issue, strong email authentication (SPF, DKIM, and DMARC) significantly boosts your sender reputation. A robust authentication setup tells Gmail that you're a legitimate sender, which can positively influence how your content is perceived. This helps avoid messages being flagged as unsolicited mail. Consider implementing a DMARC policy if you haven't already, or review your existing one using our simple guide to DMARC, SPF, and DKIM.
Maintain a healthy sender reputation
Regularly monitor your email sending practices to prevent issues that could lead to blocklisting (or blacklisting). Keep your mailing lists clean, remove inactive subscribers, and avoid sending to known spam traps. A consistent positive sending history will build trust with mailbox providers like Gmail, reducing the likelihood of your emails being flagged.
Views from the trenches
Best practices
Always validate all URLs in your email campaigns to ensure they are secure (HTTPS) and not associated with any malicious activity.
Replace email addresses in tracking URLs with anonymous subscriber IDs or hashed values to avoid triggering Gmail's content filters.
Regularly review your email content for suspicious patterns, unusual attachments, or aggressive spam trigger words that could lead to blocking.
Implement strong email authentication (SPF, DKIM, DMARC) and monitor your DMARC reports to ensure proper alignment and identify authentication failures.
Common pitfalls
Ignoring bounce messages and continuing to send emails with the same problematic content, which can further damage your sender reputation.
Using generic, low-reputation link shorteners that are frequently abused by spammers, increasing the risk of content-based blocking.
Sending emails with attachments that are on Gmail's blocked file type list or are excessively compressed, triggering security warnings.
Failing to monitor your sender reputation and not proactively addressing issues like high spam complaints or being listed on a blocklist.
Expert tips
Test problematic emails using an email deliverability tester to see how different mailbox providers react to your content and links.
Segment your audience and personalize content to reduce the likelihood of generic spam triggers and improve engagement metrics.
Keep an eye on industry news and updates from major mailbox providers like Google and Yahoo, as their filtering rules can change.
Consider using a reputable email service provider (ESP) that actively manages IP reputation and follows best practices for email deliverability.
Expert view
Expert from Email Geeks says to immediately examine the email content, especially links, as a domain hosting phishing or malware is a common cause for this bounce.
2021-08-27 - Email Geeks
Marketer view
Marketer from Email Geeks says that link shorteners could also be a cause for these types of bounces, prompting further investigation.
2021-08-27 - Email Geeks
Key takeaways for reliable email delivery
The 552 5.7.0 bounce reason from Gmail is a clear indicator that your email content, particularly its links or attachments, is triggering Gmail's security filters. This is a serious issue that demands immediate attention to prevent further deliverability problems and potential damage to your sender reputation.
By diligently reviewing your email content, especially how you handle tracking links and personal data in URLs, and by maintaining robust authentication and sender hygiene, you can significantly reduce these bounces. Proactive monitoring and adaptation to mailbox provider policies are key to ensuring your messages consistently reach the inbox.
