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
| Category | Code | Enhanced Code | Definition |
|---|---|---|---|
Blocked | 554 | 5.2.3 | Your email was blocked due to a policy or rule that prevents its delivery. This could relate to mailbox quotas, email size limitations, or specific policies set by the recipient's organization. |
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.
| Category | Code | Enhanced Code | Definition |
|---|---|---|---|
DMARC | 509 | 5.7.509 | The message was rejected by the recipient's email provider for failing DMARC checks. Ensure that the "From" header matches the SPF/DKIM-validated domains. |
DMARC | 550 | 5.0.0 | The message was rejected due to failing DMARC. Confirm that the "From" header domain aligns with the SPF/DKIM records. |
DMARC | 550 | 5.7.20 | The message did not pass DMARC validation. Ensure domain alignment between "From" header and SPF/DKIM settings. |
DMARC | 550 | 5.7.26 | DMARC validation failed. The "From" domain does not match the authenticated domains. |
DMARC | 550 | 5.7.5 | The email was blocked as it did not pass DMARC validation. Confirm the "From" domain alignment. |
DMARC | 550 | 5.7.509 | The recipient's server blocked the message due to DMARC non-compliance. Ensure proper domain authentication. |
DMARC | 550 | 5.7.6 | DMARC failure detected. Verify domain alignment between "From" header and validated domains. |
DMARC | 550 | 5.7.8 | The message was rejected for failing DMARC policy checks. Ensure SPF/DKIM configuration aligns with the sending domain. |
DMARC | 550 | 5.7.9 | The email was not accepted due to DMARC validation failure. Check domain configurations. |
DMARC | 550 | Missing | The message was blocked due to missing or incorrect DMARC validation. Ensure the "From" domain aligns correctly. |
DMARC | 553 | - | The recipient's provider rejected the message for DMARC non-compliance. Verify alignment of SPF/DKIM settings. |
DMARC | 554 | 5.0.0 | Failed DMARC check. Confirm the "From" domain matches your authenticated domains. |
DMARC | 554 | 5.7.5 | DMARC authentication failed. Adjust your SPF/DKIM configurations to pass the check. |
DMARC | 555 | 5.7.5 | The recipient's server blocked the email due to DMARC policy failure. Confirm domain settings for SPF/DKIM. |
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.
| Category | Code | Enhanced Code | Definition |
|---|---|---|---|
Invalid Address | 450 | 4.1.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 500 | 5.0.0 | The recipient's email address is invalid or does not exist. |
Invalid Address | 500 | 5.1.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 501 | 5.1.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 501 | 5.1.3 | The recipient's email address is invalid or does not exist. |
Invalid Address | 501 | 5.1.3 | The recipient's email address is invalid or does not exist. |
Invalid Address | 501 | 5.5.4 | The recipient's email address is invalid or does not exist. |
Invalid Address | 501 | 5.7.0 | The recipient's email address is invalid or does not exist. |
Invalid Address | 505 | - | The recipient's email address is invalid or does not exist. |
Invalid Address | 508 | 5.1.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 511 | 5.1.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 511 | - | The recipient's email address is invalid or does not exist. |
Invalid Address | 521 | 5.3.2 | The recipient's email address is invalid or does not exist. |
Invalid Address | 522 | 5.7.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 525 | 5.7.13 | The recipient's email address is invalid or does not exist. |
Invalid Address | 540 | 5.7.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 542 | - | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.0.0 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.0.0 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.0.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.0.350 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.1.0 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.1.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.1.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.1.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.1.10 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.1.10 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.1.181 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.1.2 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.1.2 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.1.351 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.1.351 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.1.6 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.2.1 | The email account that you tried to reach is inactive. |
Invalid Address | 550 | 5.2.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.2.14 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.2.5 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.3.0 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.3.2 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.3.2 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.4.310 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.4.312 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.4.350 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.4.355 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.5.0 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.5.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.5.2 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.7.0 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.7.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.7.100 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.7.13 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | 5.8.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | - | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | - | The recipient's email address is either invalid or does not exist and is already on the bounce list. Please revalidate the email address and try again. |
Invalid Address | 550 | - | The recipient's email address is invalid or does not exist. |
Invalid Address | 550 | - | These errors are originating from the recipient's end due to a misconfiguration or an outage on their MX server. |
Invalid Address | 551 | 5.1.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 551 | 5.1.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 551 | - | The recipient's email address is invalid or does not exist. |
Invalid Address | 552 | 5.1.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 553 | 5.1.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 553 | 5.1.3 | The recipient's email address is invalid or does not exist. |
Invalid Address | 553 | 5.3.0 | The recipient's email address is invalid or does not exist. |
Invalid Address | 553 | 5.3.0 | The recipient's email address is invalid or does not exist. |
Invalid Address | 553 | 5.5.3 | The recipient's email address is invalid or does not exist. |
Invalid Address | 553 | 5.7.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 553 | 5.7.2 | The recipient's email address is invalid or does not exist. |
Invalid Address | 554 | 5.0.0 | The recipient's email address is invalid or does not exist. |
Invalid Address | 554 | 5.1.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 554 | 5.1.2 | The recipient's email address is invalid or does not exist. |
Invalid Address | 554 | 5.2.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 554 | 5.2.2 | The recipient's email address is invalid or does not exist. |
Invalid Address | 554 | 5.5.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 554 | 5.7.1 | The recipient's email address is invalid or does not exist. |
Invalid Address | 554 |
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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.
| Category | Code | Enhanced Code | Definition |
|---|---|---|---|
Mailbox | 450 | 4.2.2 | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 452 | - | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 498 | - | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 511 | - | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 516 | 5.1.6 | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 522 | 5.2.2 | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 550 | 4.2.2 | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 550 | 5.0.350 | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 550 | 5.2.0 | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 550 | 5.2.2 | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 550 | 5.4.6 | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 550 | 5.5.0 | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 550 | 5.5.1 | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 552 | 5.1.1 | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 552 | 5.2.1 | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 552 | 5.5.2 | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 552 | - | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 553 | 5.3.1 | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
Mailbox | 554 | 5.1.1 | The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address. |
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.
| Category | Code | Enhanced Code | Definition |
|---|---|---|---|
Mailbox Full | 452 | 4.1.1 | The recipient's mailbox is full and unable to accept additional emails. |
Mailbox Full | 452 | 4.2.2 | The recipient's mailbox is full and cannot receive further emails. |
Mailbox Full | 550 | 5.2.2 | The recipient's mailbox is full and cannot accept new emails. |
Mailbox Full | 552 | 5.2.2 | The recipient's mailbox has reached its capacity and cannot accept additional emails. |
Mailbox Full | 552 | 5.2.2 | The recipient's mailbox is full and cannot accept new emails. |
Mailbox Full | 552 | - | The recipient's mailbox is full and cannot accommodate new emails. |
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.
Category | Code | Enhanced Code | Definition |
|---|---|---|---|
Rate Limit | 221 | - | The recipient's server has rejected your email due to an excessive volume of messages being sent too quickly. It is advised to contact the recipient through an alternative communication method. |
Rate Limit | 550 | 4.2.1 | The recipient's server has rejected your email, citing an overload of incoming messages. Please consider contacting the recipient via alternative methods. |
Rate Limit | 550 | 5.2.1 | The recipient's server has denied your email due to receiving too many messages in a short time. Please reach out through other means to inform the recipient. |
Rate Limit | 550 | 5.2.122 | The recipient's server has rejected your email due to excessive email traffic. Contact the recipient using an alternative method. |
Rate Limit | 554 | 5.2.121 | The recipient's server has denied your email due to rate limits. It is recommended to contact the recipient through alternative channels. |
Rate Limit | 554 | 5.2.122 | The recipient's server has rejected your email because it has received too many messages in a short timeframe. Please use an alternative communication method to contact the recipient. |
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.
| Category | Code | Enhanced Code | Definition |
|---|---|---|---|
Recipient Error | 450 | - | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 502 | - | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 503 | - | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 510 | - | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 521 | 5.3.0 | Cloudflare’s email routing service indicates that the message encountered an issue related to Cloudflare’s email routing or processing. |
Recipient Error | 530 | 5.3.0 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 530 | 5.7.0 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 530 | 5.7.1 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 530 | 5.7.57 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 535 | - | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 541 | 5.4.1 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 4.4.0 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 4.4.2 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 4.4.7 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.1.3 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.1.9 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.3.5 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.4.103 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.4.108 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.4.142 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.4.300 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.4.315 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.4.316 | The mail server was unable to deliver the message after repeated attempts. The message eventually "expired" after exceeding the time limit set for retries. |
Recipient Error | 550 | 5.4.317 | The mail server was unable to deliver the message after repeated attempts. The message eventually "expired" after exceeding the time limit set for retries. |
Recipient Error | 550 | 5.4.4 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.105 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.124 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.128 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.129 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.133 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.134 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.136 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.193 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.230 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.367 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.51 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.520 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.54 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.64 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.703 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.705 | The recipient's tenant in Microsoft 365 (or Office 365) has exceeded a specific limit or threshold, leading to the rejection of further email deliveries. |
Recipient Error | 550 | 5.7.900 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.902 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.929 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method. |
Recipient Error | 550 | 5.7.987 | The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative |
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.
| Category | Code | Enhanced Code | Definition |
|---|---|---|---|
Rejection | 450 | 4.1.8 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 501 | 5.1.0 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 501 | 5.1.7 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 501 | 5.1.8 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 501 | 5.2.0 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 501 | NA | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 533 | 5.7.1 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 550 | 5.1.0 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 550 | 5.1.7 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 550 | 5.1.8 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 550 | 5.2.3 | The email message exceeds the recipient's size limit. |
Rejection | 550 | 5.4.0 | The message was bounced due to exceeding the maximum number of server hops. This often results from mail loops or passing through too many servers. |
Rejection | 550 | 5.4.12 | The message was bounced due to exceeding the maximum number of server hops. This often results from mail loops or passing through too many servers. |
Rejection | 550 | 5.4.14 | The message was bounced due to exceeding the maximum number of server hops. This often results from mail loops or passing through too many servers. |
Rejection | 550 | 5.4.6 | The recipient's email provider detected a mail loop, resulting in a block. |
Rejection | 550 | 5.5.2 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 550 | 5.7.13 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 550 | 5.7.21 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 550 | 5.7.23 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 550 | 5.7.24 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 550 | 5.7.26 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 550 | 5.7.27 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 550 | 5.7.368 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 550 | 5.7.57 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 553 | 5.1.8 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 554 | 5.1.8 | The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider. |
Rejection | 554 | NA | The domain or email has a poor reputation, or the domain in the MAIL FROM address appears to be invalid. |
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.
- 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.
- 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.
- 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.
- 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.
- 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.
By following these guidelines, you can enhance your sender reputation and improve your email deliverability rates.