This guide covers the errors you may encounter when sending emails through the CRM. Each error has a corresponding SMTP response, identified by a Category, Error Code, and Status Code. You'll also find explanations of what each code means, why it happens, and how to fix it.
Error Categories and Definitions
Blocked
CategoryCodeEnhanced CodeDefinitionBlocked5545.2.3Your 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 organisation.
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 resolve 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.
CategoryCodeEnhanced CodeDefinitionDMARC5095.7.509The message was rejected by the recipient's email provider for failing DMARC checks. Ensure that the "From" header matches the SPF/DKIM-validated domains.DMARC5505.0.0The message was rejected due to failing DMARC. Confirm that the "From" header domain aligns with the SPF/DKIM records.DMARC5505.7.20The message did not pass DMARC validation. Ensure domain alignment between "From" header and SPF/DKIM settings.DMARC5505.7.26DMARC validation failed. The "From" domain does not match the authenticated domains.DMARC5505.7.5The email was blocked as it did not pass DMARC validation. Confirm the "From" domain alignment.DMARC5505.7.509The recipient's server blocked the message due to DMARC non-compliance. Ensure proper domain authentication.DMARC5505.7.6DMARC failure detected. Verify domain alignment between "From" header and validated domains.DMARC5505.7.8The message was rejected for failing DMARC policy checks. Ensure SPF/DKIM configuration aligns with the sending domain.DMARC5505.7.9The email was not accepted due to DMARC validation failure. Check domain configurations.DMARC550MissingThe message was blocked due to missing or incorrect DMARC validation. Ensure the "From" domain aligns correctly.DMARC553-The recipient's provider rejected the message for DMARC non-compliance. Verify alignment of SPF/DKIM settings.DMARC5545.0.0Failed DMARC check. Confirm the "From" domain matches your authenticated domains.DMARC5545.7.5DMARC authentication failed. Adjust your SPF/DKIM configurations to pass the check.DMARC5555.7.5The recipient's server blocked the email due to DMARC policy failure. Confirm domain settings for SPF/DKIM.
Invalid Address
This error means the email was sent to an address that doesn't exist or has been typed incorrectly. The recipient may have given you an invalid address, or there's a typo in the email. Use an email validation service to check addresses before sending to avoid this.
CategoryCodeEnhanced CodeDefinitionInvalid Address4504.1.1The recipient's email address is invalid or does not exist.Invalid Address5005.0.0The recipient's email address is invalid or does not exist.Invalid Address5005.1.1The recipient's email address is invalid or does not exist.Invalid Address5015.1.1The recipient's email address is invalid or does not exist.Invalid Address5015.1.3The recipient's email address is invalid or does not exist.Invalid Address5015.1.3The recipient's email address is invalid or does not exist.Invalid Address5015.5.4The recipient's email address is invalid or does not exist.Invalid Address5015.7.0The recipient's email address is invalid or does not exist.Invalid Address505-The recipient's email address is invalid or does not exist.Invalid Address5085.1.1The recipient's email address is invalid or does not exist.Invalid Address5115.1.1The recipient's email address is invalid or does not exist.Invalid Address511-The recipient's email address is invalid or does not exist.Invalid Address5215.3.2The recipient's email address is invalid or does not exist.Invalid Address5225.7.1The recipient's email address is invalid or does not exist.Invalid Address5255.7.13The recipient's email address is invalid or does not exist.Invalid Address5405.7.1The recipient's email address is invalid or does not exist.Invalid Address542-The recipient's email address is invalid or does not exist.Invalid Address5505.0.0The recipient's email address is invalid or does not exist.Invalid Address5505.0.0The recipient's email address is invalid or does not exist.Invalid Address5505.0.1The recipient's email address is invalid or does not exist.Invalid Address5505.0.350The recipient's email address is invalid or does not exist.Invalid Address5505.1.0The recipient's email address is invalid or does not exist.Invalid Address5505.1.1The recipient's email address is invalid or does not exist.Invalid Address5505.1.1The recipient's email address is invalid or does not exist.Invalid Address5505.1.1The recipient's email address is invalid or does not exist.Invalid Address5505.1.10The recipient's email address is invalid or does not exist.Invalid Address5505.1.10The recipient's email address is invalid or does not exist.Invalid Address5505.1.181The recipient's email address is invalid or does not exist.Invalid Address5505.1.2The recipient's email address is invalid or does not exist.Invalid Address5505.1.2The recipient's email address is invalid or does not exist.Invalid Address5505.1.351The recipient's email address is invalid or does not exist.Invalid Address5505.1.351The recipient's email address is invalid or does not exist.Invalid Address5505.1.6The recipient's email address is invalid or does not exist.Invalid Address5505.2.1The email account that you tried to reach is inactive.Invalid Address5505.2.1The recipient's email address is invalid or does not exist.Invalid Address5505.2.14The recipient's email address is invalid or does not exist.Invalid Address5505.2.5The recipient's email address is invalid or does not exist.Invalid Address5505.3.0The recipient's email address is invalid or does not exist.Invalid Address5505.3.2The recipient's email address is invalid or does not exist.Invalid Address5505.3.2The recipient's email address is invalid or does not exist.Invalid Address5505.4.310The recipient's email address is invalid or does not exist.Invalid Address5505.4.312The recipient's email address is invalid or does not exist.Invalid Address5505.4.350The recipient's email address is invalid or does not exist.Invalid Address5505.4.355The recipient's email address is invalid or does not exist.Invalid Address5505.5.0The recipient's email address is invalid or does not exist.Invalid Address5505.5.1The recipient's email address is invalid or does not exist.Invalid Address5505.5.2The recipient's email address is invalid or does not exist.Invalid Address5505.7.0The recipient's email address is invalid or does not exist.Invalid Address5505.7.1The recipient's email address is invalid or does not exist.Invalid Address5505.7.100The recipient's email address is invalid or does not exist.Invalid Address5505.7.13The recipient's email address is invalid or does not exist.Invalid Address5505.8.1The recipient's email address is invalid or does not exist.Invalid Address550-The recipient's email address is invalid or does not exist.Invalid Address550-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 Address550-The recipient's email address is invalid or does not exist.Invalid Address550-These errors are originating from the recipient's end due to a misconfiguration or an outage on their MX server.Invalid Address5515.1.1The recipient's email address is invalid or does not exist.Invalid Address5515.1.1The recipient's email address is invalid or does not exist.Invalid Address551-The recipient's email address is invalid or does not exist.Invalid Address5525.1.1The recipient's email address is invalid or does not exist.Invalid Address5535.1.1The recipient's email address is invalid or does not exist.Invalid Address5535.1.3The recipient's email address is invalid or does not exist.Invalid Address5535.3.0The recipient's email address is invalid or does not exist.Invalid Address5535.3.0The recipient's email address is invalid or does not exist.Invalid Address5535.5.3The recipient's email address is invalid or does not exist.Invalid Address5535.7.1The recipient's email address is invalid or does not exist.Invalid Address5535.7.2The recipient's email address is invalid or does not exist.Invalid Address5545.0.0The recipient's email address is invalid or does not exist.Invalid Address5545.1.1The recipient's email address is invalid or does not exist.Invalid Address5545.1.2The recipient's email address is invalid or does not exist.Invalid Address5545.2.1The recipient's email address is invalid or does not exist.Invalid Address5545.2.2The recipient's email address is invalid or does not exist.Invalid Address5545.5.1The recipient's email address is invalid or does not exist.Invalid Address5545.7.1The recipient's email address is invalid or does not exist.Invalid Address554
Mailbox Issues
This type of bounce means the recipient's email address is invalid or their domain has no mailbox set up to receive emails. To keep things running smoothly:
- Validate email addresses before sending campaigns using an email validation service.
- Double-check for any typos in the recipient's email address.
- Verify that the recipient's domain is active and able to receive emails.
CategoryCodeEnhanced CodeDefinitionMailbox4504.2.2The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox452-The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox498-The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox511-The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox5165.1.6The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox5225.2.2The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox5504.2.2The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox5505.0.350The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox5505.2.0The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox5505.2.2The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox5505.4.6The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox5505.5.0The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox5505.5.1The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox5525.1.1The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox5525.2.1The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox5525.5.2The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox552-The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox5535.3.1The recipient's domain has no mailbox and does not accept mail. Please send to a valid email address.Mailbox5545.1.1The 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 the recipient's inbox has hit its storage limit and can't accept new messages. This is usually temporary and will often resolve itself once the recipient clears some space or their storage is increased. To work around it:
- Wait a while before resending, as the recipient may clear their inbox in the meantime.
- Try reaching the recipient another way, such as by phone or social media, to let them know their mailbox is full.
CategoryCodeEnhanced CodeDefinitionMailbox Full4524.1.1The recipient's mailbox is full and unable to accept additional emails.Mailbox Full4524.2.2The recipient's mailbox is full and cannot receive further emails.Mailbox Full5505.2.2The recipient's mailbox is full and cannot accept new emails.Mailbox Full5525.2.2The recipient's mailbox has reached its capacity and cannot accept additional emails.Mailbox Full5525.2.2The recipient's mailbox is full and cannot accept new emails.Mailbox Full552-The recipient's mailbox is full and cannot accommodate new emails.
Rate Limit Issues
Rate limit bounces happen when you're sending too many emails to the recipient's server too quickly, triggering its anti-spam filters and temporarily blocking your messages. To address this:
- Throttle your sending rate by slowing down how frequently you send to the recipient, so you're not overwhelming their server.
- Use email queues to dispatch messages in smaller batches over time, reducing the overall load.
If the problem persists, it's worth contacting the recipient's IT team to ask about whitelisting your sending domain.
CategoryCodeEnhanced CodeDefinitionRate Limit221-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 Limit5504.2.1The recipient's server has rejected your email, citing an overload of incoming messages. Please consider contacting the recipient via alternative methods.Rate Limit5505.2.1The 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 Limit5505.2.122The recipient's server has rejected your email due to excessive email traffic. Contact the recipient using an alternative method.Rate Limit5545.2.121The recipient's server has denied your email due to rate limits. It is recommended to contact the recipient through alternative channels.Rate Limit5545.2.122The 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 mean the recipient's server is blocking incoming emails from external sources. If the rejection keeps happening, get in touch with the recipient through another channel.
CategoryCodeEnhanced CodeDefinitionRecipient Error450-The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error502-The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error503-The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error510-The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5215.3.0Cloudflare's email routing service indicates that the message encountered an issue related to Cloudflare's email routing or processing.Recipient Error5305.3.0The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5305.7.0The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5305.7.1The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5305.7.57The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error535-The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5415.4.1The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5504.4.0The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5504.4.2The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5504.4.7The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.1.3The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.1.9The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.3.5The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.4.103The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.4.108The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.4.142The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.4.300The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.4.315The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.4.316The mail server was unable to deliver the message after repeated attempts. The message eventually "expired" after exceeding the time limit set for retries.Recipient Error5505.4.317The mail server was unable to deliver the message after repeated attempts. The message eventually "expired" after exceeding the time limit set for retries.Recipient Error5505.4.4The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.105The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.124The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.128The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.129The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.133The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.134The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.136The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.193The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.230The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.367The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.51The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.520The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.54The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.64The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.703The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.705The 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 Error5505.7.900The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.902The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.929The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.Recipient Error5505.7.987The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.
Rejection Error Codes
Rejection error codes give useful insight into why emails aren't getting through, covering things like DNS records, server configuration, and email reputation.
CategoryCodeEnhanced CodeDefinitionRejection4504.1.8The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5015.1.0The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5015.1.7The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5015.1.8The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5015.2.0The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection501NAThe sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5335.7.1The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5505.1.0The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5505.1.7The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5505.1.8The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5505.2.3The email message exceeds the recipient's size limit.Rejection5505.4.0The message was bounced due to exceeding the maximum number of server hops. This often results from mail loops or passing through too many servers.Rejection5505.4.12The message was bounced due to exceeding the maximum number of server hops. This often results from mail loops or passing through too many servers.Rejection5505.4.14The message was bounced due to exceeding the maximum number of server hops. This often results from mail loops or passing through too many servers.Rejection5505.4.6The recipient's email provider detected a mail loop, resulting in a block.Rejection5505.5.2The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5505.7.13The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5505.7.21The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5505.7.23The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5505.7.24The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5505.7.26The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5505.7.27The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5505.7.368The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5505.7.57The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5535.1.8The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection5545.1.8The sending domain lacks valid DNS records. Please verify the domain and ensure all necessary DNS records are configured with your DNS provider.Rejection554NAThe 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 for suspected spam or malicious content, here's how to improve your sender reputation and get things back on track:
- Check IP and Domain Blacklists: Check whether your IP or domain is listed on any blacklists using Blacklist Check Tools. If it is, follow the delisting process provided by the relevant blacklist service.
- Ensure Proper DNS Configuration: To ensure proper email authentication, configure your SPF records to authorise your email servers, implement DKIM signatures to authenticate your emails, and set up DMARC policies to protect against email spoofing. 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. Start with smaller batches and gradually increase the volume over time.
- Clean and Segment Email Lists: Remove inactive or invalid email addresses to reduce bounce rates. Use email validation tools to verify addresses before launching campaigns. Track spam complaints and promptly remove recipients who report your emails as spam.
- Check Email Content and Follow Best Practices: Avoid spammy phrases such as "Congratulations!!!" or "Act Now!" in subject lines. Maintain a balanced image-to-text ratio, ensuring your emails have adequate text content alongside images. Make sure all links are safe and not blacklisted. Include a clear unsubscribe link in all marketing emails, and comply with regulations such as CAN-SPAM and GDPR.
Following these steps will help improve your sender reputation and email deliverability over time.