Email Bounce Classification

This guide provides an overview of potential errors you may encounter when sending messages through our service. Each error is associated with a specific SMTP response, characterized by a unique Category, Error Code, and Status Code. You will also find detailed explanations of these codes, including their underlying causes and practical solutions to resolve them efficiently. Leverage this resource to quickly diagnose and address any email delivery issues you may experience.

Error Categories and Definitions

Blocked

DMARC Errors

DMARC (Domain-based Message Authentication, Reporting & Conformance) errors occur when a message fails authentication checks because the "From" header does not align with validated SPF/DKIM domains. Here are some tips to resole DMARC Errors:

• Ensure the "From" address aligns with your sending domain.
• Verify that both SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) are correctly configured for your domain.
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Invalid Address

This error indicates that the email was sent to a non-existent or incorrectly typed email address. The recipient may have provided an invalid address, or there could be a typo in the email. Utilize an email validation service to ensure the accuracy of email addresses before sending messages to resolve this error.

Mailbox Issues

This type of bounce indicates that the recipient's email address is invalid or their domain does not have a mailbox to receive emails. To ensure successful email delivery, it is important to:

• Validate email addresses before sending campaigns by using an email validation service.
• Double-check for any typographical errors in the recipient's email address to avoid issues.
• Verify that the recipient's domain is active and capable of receiving emails to prevent delivery failures.
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Mailbox Full

A "Mailbox Full" bounce means that the recipient's inbox has reached its storage capacity and cannot accept new messages. This issue is usually temporary and may resolve when the recipient clears space or their mailbox size is increased. To resolve issues with a full mailbox:

• Wait and retry by allowing some time before resending your email, as the recipient may clear their mailbox.
• Contact the recipient through alternative methods, such as phone or social media, to inform them of their full mailbox and encourage them to address the issue.
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Rate Limit Issues

Rate limit bounces occur when you are sending too many emails to the recipient's server too quickly. This can trigger the server's anti-spam filters, causing your emails to be temporarily blocked. To address rate limit issues:

• Consider throttling your sending rate by slowing down the frequency of emails sent to the recipient, ensuring you do not overwhelm their server. 
• Use email queues can help by dispatching messages in smaller batches over time, reducing the overall load. 

If the issue persists, it may be beneficial to contact the recipient's IT team to request assistance with whitelisting your sending domain, which can help prevent future rate limit rejections.

Recipient Error

These errors suggest that the recipient's server is blocking incoming emails from external sources, preventing successful delivery. In cases where the email rejection continues, it is recommended to reach out to the recipient via an alternative communication method.

Rejection Error Codes

Rejection Error Codes provide crucial insights into why emails may not be successfully delivered. Understanding these error codes can help diagnose issues with DNS records, server configurations, and email reputation. 

Sender Reputation

If your emails are being blocked due to potential spam or malicious content, follow these steps to improve your sender reputation and ensure successful delivery:

• Check IP and Domain Blacklists: Verify if your IP or domain is listed on any blacklists using Blacklist Check Tools. If found, follow the specific delisting procedures provided by the blacklist service.
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• Ensure Proper DNS Configuration: To ensure proper email authentication, configure your SPF records to authorize your email servers, implement DKIM signatures to authenticate your emails, and set up DMARC policies to protect against email spoofing. Additionally, use tools like MXToolbox to validate your SPF, DKIM, and DMARC records.
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• Monitor and Improve Email Reputation: Use Microsoft SNDS (Smart Network Data Services) to check the status of your IP addresses with services like Outlook and Hotmail, and access Google Postmaster Tools to track your domain’s performance and reputation with Gmail.
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• Send Smaller Email Batches to Build Reputation: To build trust with email providers, avoid sending large volumes of emails from a new or inactive IP/domain. Begin with smaller batches and gradually increase the volume over time.
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• Clean and Segment Email Lists: To maintain a healthy email list, remove inactive or invalid email addresses to reduce bounce rates. Use email validation tools to verify addresses before launching campaigns. Also, monitor feedback by tracking spam complaints and promptly removing recipients who report your emails as spam.
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• Check Email Content and Follow Best Practices: To improve email deliverability, avoid spammy phrases such as “Congratulations!!!” or “Act Now!” in subject lines. Maintain a balanced image-to-text ratio, ensuring that your emails have adequate text content along with images. Ensure all links are safe and not blacklisted. Additionally, comply with anti-spam regulations by including a clear unsubscribe link in all marketing emails, adhering to laws like CAN-SPAM and GDPR.
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By following these guidelines, you can enhance your sender reputation and improve your email deliverability rates.