What is 550-5.7. 26 Error and How to Resolve it?

550-5.7.26 error

Email remains a cornerstone of communication, especially in the business and IT sectors. It’s a tool that bridges gaps between continents, fuels business deals, and facilitates daily operations. However, technical errors, including the 550-5.7.26 error, can sometimes disrupt this seamless communication.

Google has officially started rolling out New Bulk Email Sender Policies for 2024, and if you are receiving a rejection notice from Google when you are sending emails to Gmail or Google Workspace accounts that looks something like this:

550-5.7.26 This mail is unauthenticated, which poses a security risk to the 550-5.7.26 sender and Gmail users, and has been blocked. The sender must 550-5.7.26 authenticate with at least one of SPF or DKIM.

This occurred because Google requires email authentication to ensure security. Without proper methods like SPF, DKIM, or DMARC, Google couldn’t confirm the email’s legitimacy, leading to rejection.

Encountering this error can be a frustrating experience, as it often prevents emails from reaching their intended recipients, leading to communication delays and potential business impacts.

Step-by-Step Guide to Resolve the 550 ‘5.7.26’ Error

Resolving the 550 ‘5.7.26’ error involves checking and correcting the configurations related to SPF, DKIM, and DMARC. Here’s a structured guide to help you through this process:

1. Checking and Correcting SPF Records

  • Verify Your SPF Record: Use an SPF record checker tool to verify if your domain has a valid SPF record.
  • Update SPF Record: If the SPF record is missing or incorrect, update it to include all mail servers used by your domain. Ensure that the record syntax is correct.
  • Limit the Number of DNS Lookups: SPF records should not exceed 10 DNS lookups. Exceeding this limit can lead to SPF failures.

2. Verifying DKIM Setup

  • Check DKIM Signature: Ensure that your email system is signing emails with a DKIM signature. You can use online tools to inspect outgoing emails for a DKIM signature.
  • Validate DKIM Record: Use a DKIM record checker to ensure that your domain’s DNS contains a correct DKIM record corresponding to the signature.
  • Correct DKIM Configuration: If you find discrepancies, update your DKIM record in your domain’s DNS settings. Ensure the selector and domain name in the DKIM signature match those in the DNS record.

3. Ensuring DMARC Alignment

  • Inspect DMARC Policy: Use a DMARC policy checker to review your domain’s DMARC settings. Ensure that the policy aligns with your email sending practices.
  • Adjust DMARC Settings: If necessary, adjust the DMARC policy to be less strict, allowing emails that fail either SPF or DKIM checks but not both, especially if you’re troubleshooting.
  • Monitor DMARC Reports: Regularly check DMARC reports for insights on your email traffic and authentication status, which can help in identifying and rectifying ongoing issues.

Tips for Non-Technical Users

  • Seek Professional Help: If you are not confident in making DNS changes, consider consulting with an email authentication expert or your domain hosting provider.
  • Use Simplified Tools: Some email service providers offer simplified interfaces or wizards to guide you through setting up SPF, DKIM, and DMARC.

By implementing these steps, you can significantly help resolve the 550-5.7.26 error, ensuring the successful delivery of your emails.

Understanding the 550-5.7.26 Error

When email communication encounters the 550-5.7.26 error, it means the recipient’s mail server has rejected your message and prevented delivery. What exactly does this error tell us?

Technical Explanation

At its core, this error is related to email authentication methods that ensure the legitimacy of an email sender. When an email fails certain authentication checks, the recipient’s server rejects it, resulting in the 550 ‘5.7.26’ error. This is a part of the server’s security measures to prevent spam and phishing attacks.

Common Scenarios

Several scenarios commonly trigger this error:

  • When the email’s origin cannot be verified as legitimate.
  • If the sender enforces strict email policies, and your email fails to meet those requirements.
  • In cases where the email does not align with certain technical standards set by the receiving server.

Understanding these scenarios is crucial for both diagnosing and resolving the issue.

Authentication Processes Involved

Three key authentication processes play a vital role in this context:

  1. SPF (Sender Policy Framework): This verifies that the sending server is authorized to send emails on behalf of the domain.
  2. DKIM (DomainKeys Identified Mail): This involves a digital signature ensuring that the content of the email remains tamper-proof from the point of sending to the point of receiving.
  3. DMARC (Domain-based Message Authentication, Reporting & Conformance): This ensures that the email aligns with the policies set by the sender’s domain and is not fraudulent.

Failure in any of these authentication steps can lead to the 550-5.7.26 error, indicating that the email was flagged as unauthenticated or potentially harmful.

Common Causes of the 550 ‘5.7.26’ Error

Identifying the root cause of the 550-5.7.26 error is crucial for effective resolution. This section explores the most frequent causes, providing insights into what might be going wrong.

SPF (Sender Policy Framework) Failures

The SPF record is a DNS (Domain Name System) text entry that lists the servers authorized to send emails on behalf of your domain. A common cause for the 550 error is a failure in SPF verification. This can occur if:

  • The SPF record is missing or improperly configured.
  • The email is sent from a server not included in the SPF record.
DKIM (DomainKeys Identified Mail) Issues

DKIM adds a digital signature to emails, which is verified against a public key in your domain’s DNS records. Issues leading to the error may involve:

  • Incorrect DKIM signature that doesn’t match the public key.
  • Missing or misconfigured DKIM records in the DNS.
DMARC (Domain-based Message Authentication, Reporting & Conformance) Alignment Problems

DMARC helps in aligning SPF and DKIM authentication, adding an additional layer of security. The 550 error can be triggered by DMARC issues such as:

  • Strict DMARC policies not met by either SPF or DKIM.
  • Misalignment between the domain in the email header and the domain in the SPF or DKIM records.

Understanding these causes is the first step in troubleshooting the 550 ‘5.7.26’ error. Once identified, the appropriate corrective measures can be taken to resolve the issue and ensure smooth email communication.


The 550 ‘5.7.26’ error can be a hurdle in seamless email communication, but understanding and addressing it is crucial for maintaining the integrity and reliability of your email correspondence. This guide aims to empower you with the knowledge and steps necessary to tackle this issue head-on. Remember, a proactive approach to email authentication and regular checks can prevent such errors and keep your communication channels clear.

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Google & Yahoo’s new bulk email sender requirements coming live on February 1, 2024. Are you ready?