Summary
The Gmail bounce error '550-5.7.1 our system has detected that this message is likely unsolicited mail' indicates that Gmail has flagged the email as potential spam. This can result from several factors, including poor sender reputation, email content that triggers spam filters, inadequate email authentication (SPF, DKIM, DMARC), sending to outdated or unengaged email lists, a sudden surge in email volume, a problematic dedicated IP address, or a missing or difficult-to-locate unsubscribe option. Resolving this issue entails improving sender reputation, auditing email content for spam indicators, implementing proper authentication, maintaining a clean email list, gradually increasing sending volume (especially for new IPs), assessing the dedicated IP's reputation (if applicable), and ensuring a clear and accessible unsubscribe mechanism. ESPs might retry delivery after a bounce, but Google won't retroactively reverse bounces.
Key findings
- Spam-like Characteristics: Gmail has detected characteristics in the email that resemble spam, leading to the block.
- Sender Reputation: A poor sender reputation is a leading cause, tied to IP address, domain, and sending behavior.
- Content Issues: The email content may contain spam trigger words, phrases, or elements that flag it as unsolicited.
- Authentication Failures: Lack of proper SPF, DKIM, and DMARC records can signal to Gmail that the email isn't trustworthy.
- Poor List Quality: Sending to old, unengaged, or invalid email addresses increases the likelihood of bounces and spam complaints.
- Volume Spikes: Sudden increases in email sending volume can trigger spam filters and lead to blocks.
- IP Reputation (Dedicated IPs): If using a dedicated IP, its reputation directly impacts deliverability.
- Unsubscribe Problems: Making it difficult to unsubscribe can lead recipients to mark emails as spam, further damaging reputation.
- Non Transient Error: A Google 550 response is not transient and should not be retried unless remediated.
Key considerations
- Check Sending Practices: Carefully review sending practices, including volume, frequency, and content.
- Implement Authentication: Verify and properly configure SPF, DKIM, and DMARC records.
- Clean Email List Regularly: Remove inactive subscribers, invalid addresses, and spam traps from the email list.
- Warm-Up IP Gradually: If using a new IP address, gradually increase sending volume to establish a positive reputation.
- Easy Unsubscribe Options: Ensure a clear and easy-to-find unsubscribe link in all emails.
- Monitor Reputation: Use tools like Google Postmaster Tools and Sender Score to monitor sender reputation.
- Content Review: Review email content to avoid spam trigger words and phrases. Use plain text versions.
- Contact ESP if Necessary: Communicate with your ESP regarding bounces and possible resolutions. Some will retry the sending of these emails.
What email marketers say
15 marketer opinions
The Gmail bounce error '550-5.7.1 our system has detected that this message is likely unsolicited mail' indicates that Gmail's system has identified the email as potential spam. This can be due to various factors including poor sender reputation, spam-like content, lack of proper email authentication (SPF, DKIM, DMARC), sending to old or unengaged email lists, sudden increases in sending volume, issues with dedicated IP addresses, or a missing or unclear unsubscribe option. Resolving this error involves improving sender reputation, reviewing email content for spam triggers, implementing proper authentication, maintaining a clean email list, gradually increasing sending volume, checking the reputation of your dedicated IP address (if applicable), and ensuring easy unsubscribe options.
Key opinions
- Sender Reputation: Poor sender reputation is a primary cause. This involves factors like IP address reputation and domain reputation.
- Spam-Like Content: Email content containing spam trigger words or phrases can flag the email as unsolicited.
- Authentication: Failing to properly configure SPF, DKIM, and DMARC records can cause deliverability issues.
- List Quality: Sending emails to old, unengaged, or invalid addresses can negatively impact deliverability.
- Sending Volume: A sudden increase in email sending volume can trigger spam filters.
- Dedicated IP Reputation: The reputation of a dedicated IP address can influence whether emails are marked as spam.
- Unsubscribe Option: A missing or difficult-to-find unsubscribe option can lead recipients to mark emails as spam.
Key considerations
- Review Sending Practices: Assess your current email sending practices to identify potential issues related to volume, frequency, and content.
- Implement Authentication: Ensure SPF, DKIM, and DMARC records are properly configured to authenticate your email.
- Clean Email List: Regularly clean your email list to remove inactive subscribers, invalid addresses, and spam traps.
- Warm-Up IP Address: Gradually warm up your IP address, especially when starting with a new IP or increasing sending volume.
- Provide Easy Unsubscribe: Ensure a clear and easy-to-find unsubscribe link in all emails.
- Monitor Reputation: Monitor your sender reputation using tools like Google Postmaster Tools or Sender Score.
- Resend Bounces: If you've had bounces due to a temporary issue, consider asking your ESP if they will retry, or resend yourself.
Marketer view
Email marketer from Litmus explains that a good list quality prevents the 550 5.7.1 error. By cleaning your list and only sending to engaged users prevents hitting spam traps and hard bounces.
27 Sep 2022 - Litmus
Marketer view
Marketer from Email Geeks shares the bounce error message being received: "550-5.7.1 [1.2.3.4 12] Our system has detected that this message is 550-5.7.1 likely unsolicited mail. To reduce the amount of spam sent to Gmail, 550-5.7.1 this message has been blocked. Please visit 550-5.7.1 <https://support.google.com/mail/?p=UnsolicitedMessageError> 550 5.7.1 for more information. m22si31676271725pjr.168 - gsmtp"
5 May 2022 - Email Geeks
What the experts say
3 expert opinions
The Gmail bounce error 550 5.7.1, indicating 'our system has detected that this message is likely unsolicited mail,' can be attributed to several factors. Primarily, it often signals that a content filter has flagged the email, suggesting a review of email content for spam-like keywords is necessary. Additionally, the error commonly points to an issue with the sender's reputation, necessitating improvements in email authentication and adherence to email marketing best practices. Moreover, the presence of old or unengaged users on mailing lists can negatively impact deliverability and trigger this error due to the resulting harm to sender reputation.
Key opinions
- Content Filters: Spam-like keywords or phrases in email content can trigger content filters, leading to the 550 5.7.1 error.
- Sender Reputation: A poor sender reputation is a common cause of the error, often stemming from inadequate email authentication or non-compliance with email marketing best practices.
- List Hygiene: Sending emails to old or unengaged users on mailing lists can negatively impact deliverability and contribute to reputation issues.
Key considerations
- Review Email Content: Thoroughly examine email content to identify and remove any spam-like keywords or phrases that may trigger content filters.
- Improve Sender Reputation: Enhance sender reputation by implementing robust email authentication protocols (SPF, DKIM, DMARC) and adhering to established email marketing best practices.
- Clean Mailing Lists: Regularly purge mailing lists of old, unengaged, or invalid email addresses to maintain a healthy sender reputation and improve deliverability.
Expert view
Expert from Word to the Wise suggests cleaning your lists from old or unengaged users. This can negatively impact the deliverability of your email and cause a 550 5.7.1 error due to reputation issues.
2 Jun 2023 - Word to the Wise
Expert view
Expert from Word to the Wise explains the 550 5.7.1 error usually means there is a problem with the sender’s reputation. It points out that improving sender reputation by authenticating your email and ensuring you are following email best practices can prevent it.
31 Mar 2025 - Word to the Wise
What the documentation says
4 technical articles
The Gmail bounce error '550-5.7.1 our system has detected that this message is likely unsolicited mail' signifies that Gmail has flagged the email as spam, stemming from issues like poor sender reputation, problematic content, lack of proper authentication, or violations of email policies. Resolving this requires improving sender reputation, ensuring compliance with anti-spam policies, carefully reviewing email content, and properly implementing email authentication methods like SPF, DKIM, and DMARC. The RFC documents provide standardized feedback about delivery problems.
Key findings
- Unsolicited Message: The core cause is that Gmail has classified the message as unsolicited, meaning it resembles spam.
- Sender Reputation: Sender reputation is a key factor influencing Gmail's spam detection.
- Email Content: The content of the email plays a significant role in determining whether it's flagged as spam.
- Authentication: Proper email authentication, including SPF, DKIM, and DMARC, is critical for deliverability.
- Policy Violation: The error may indicate a violation of Gmail's or other relevant email policies.
- Standardized Feedback: SMTP status codes provide feedback about delivery issues and help identify areas for improvement.
Key considerations
- Improve Reputation: Take steps to improve your sender reputation, such as maintaining consistent sending practices and avoiding spam traps.
- Review Content: Carefully review your email content to ensure it doesn't contain spam-like elements or trigger spam filters.
- Implement Authentication: Verify that SPF, DKIM, and DMARC records are correctly configured for your domain.
- Check Policies: Review and adhere to Gmail's and other relevant email policies to avoid policy violations.
Technical article
Documentation from Google Support explains the 550 5.7.1 error indicates Gmail detected the message as unsolicited. Google recommends checking your sending practices, ensuring proper authentication (SPF, DKIM, DMARC), and reviewing their bulk sender guidelines.
14 Jun 2025 - Google Support
Technical article
Documentation from RFC Editor explains that SMTP enhanced status codes, like 5.7.1, provide standardized feedback about delivery problems. It points to security or policy issues that prevent message delivery and the full RFC describes the meaning of each number.
16 Jan 2023 - RFC Editor
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