Bounce Classification Codes and Definitions

Blocked

Category	Code	Enhanced Code	Definition
Blocked	554	5.2.3	Your email was blocked because there's a policy or rule in place that's preventing the email from being delivered. This could be related to mailbox quotas, email size limits, or specific policies configured by the organization

---

DMARC

The message failed DMARC authentication because the "From" header doesn't align with the validated SPF/DKIM domains.

Resolution Tips:

• Ensure the "From" address matches the sending domain.

• Verify that both SPF and DKIM are correctly configured for your sending domain.

Category	Code	Enhanced Code	Definition
DMARC	509	5.7.509	The message was rejected by recepients email provider because it did not pass the DMARC. Ensure that the "From" header domain matches or aligns with the SPF/DKIM-validated domains.
DMARC	550	5.0.0	The message was rejected by recepients email provider because it did not pass the DMARC. Ensure that the "From" header domain matches or aligns with the SPF/DKIM-validated domains.
DMARC	550	5.7.20	The message was rejected by recepients email provider because it did not pass the DMARC. Ensure that the "From" header domain matches or aligns with the SPF/DKIM-validated domains.
DMARC	550	5.7.26	The message was rejected by recepients email provider because it did not pass the DMARC. Ensure that the "From" header domain matches or aligns with the SPF/DKIM-validated domains.
DMARC	550	5.7.5	The message was rejected by recepients email provider because it did not pass the DMARC. Ensure that the "From" header domain matches or aligns with the SPF/DKIM-validated domains.
DMARC	550	5.7.5	The message was rejected by recepients email provider because it did not pass the DMARC. Ensure that the "From" header domain matches or aligns with the SPF/DKIM-validated domains.
DMARC	550	5.7.509	The message was rejected by recepients email provider because it did not pass the DMARC. Ensure that the "From" header domain matches or aligns with the SPF/DKIM-validated domains.
DMARC	550	5.7.6	The message was rejected by recepients email provider because it did not pass the DMARC. Ensure that the "From" header domain matches or aligns with the SPF/DKIM-validated domains.
DMARC	550	5.7.8	The message was rejected by recepients email provider because it did not pass the DMARC. Ensure that the "From" header domain matches or aligns with the SPF/DKIM-validated domains.
DMARC	550	5.7.9	The message was rejected by recepients email provider because it did not pass the DMARC. Ensure that the "From" header domain matches or aligns with the SPF/DKIM-validated domains.
DMARC	550	Missing	The message was rejected by recepients email provider because it did not pass the DMARC. Ensure that the "From" header domain matches or aligns with the SPF/DKIM-validated domains.
DMARC	553	-	The message was rejected by recepients email provider because it did not pass the DMARC. Ensure that the "From" header domain matches or aligns with the SPF/DKIM-validated domains.
DMARC	554	5.0.0	The message was rejected by recepients email provider because it did not pass the DMARC. Ensure that the "From" header domain matches or aligns with the SPF/DKIM-validated domains.
DMARC	554	5.7.5	The message was rejected by recepients email provider because it did not pass the DMARC. Ensure that the "From" header domain matches or aligns with the SPF/DKIM-validated domains.
DMARC	555	5.7.5	The message was rejected by recepients email provider because it did not pass the DMARC. Ensure that the "From" header domain matches or aligns with the SPF/DKIM-validated domains.

---

Invalid address

Indicates that you attempted to send a message to an address that does not exist. The contact could have provided a false address or made a typo in the address.

Resolution Tips:

Validate emails with Email Validation

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	5.7.7	The recipient's email address is invalid or does not exist.
Invalid address	554	-	The recipient's email address is invalid or does not exist.
Invalid address	556	5.1.1	The recipient's email address is invalid or does not exist.
Invalid address	572	-	The recipient's email address is invalid or does not exist.
Invalid address	577	5.1.1	The recipient's email address is invalid or does not exist.
Invalid address	585	5.1.1	The recipient's email address is invalid or does not exist.
Invalid address	605	-	The recipient's email address is already on the bounce list. Please revalidate the email address and try again.
Invalid address	612	-	These errors are originating from the recipient's end due to a misconfiguration or an outage on their MX server.

---

Mailbox

Indicates that you attempted to send a message to an address that does not have a mailbox.

Resolution Tips:

Validate emails with Email Validation

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 valid email address.
Mailbox	452	-	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	498	-	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	511	-	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	516	5.1.6	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	522	5.2.2	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	550	4.2.2	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	550	5.0.350	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	550	5.2.0	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	550	5.2.2	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	550	5.4.6	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	550	5.5.0	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	550	5.5.1	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	552	5.1.1	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	552	5.2.1	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	552	5.5.2	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	552	-	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	553	5.3.1	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.
Mailbox	554	5.1.1	The recipient's domain has no mailbox and does not accept mail. Please send to valid email address.

---

Mailbox Full

A "Mailbox Full" bounce occurs when the recipient's inbox has reached its storage limit and cannot accept new messages. This is often a temporary issue, and once the recipient clears space or the mailbox size is increased, emails can be delivered.

Category	Code	Enhanced Code	Definition
Mailbox Full	452	4.1.1	The recipient's mailbox is full and cannot accept new emails.
Mailbox Full	452	4.2.2	The recipient's mailbox is full and cannot accept new 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 is full and cannot accept new 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 accept new emails.

---

Rate Limit

Category	Code	Enhanced Code	Definition
Rate Limit	221	-	The recipient's server has denied your email. You’re sending mail to is getting too many emails too fast. Please contact the recipient using an alternative method.
Rate Limit	550	4.2.1	The recipient's server has denied your email. You’re sending mail to is getting too many emails too fast. Please contact the recipient using an alternative method.
Rate Limit	550	5.2.1	The recipient's server has denied your email. You’re sending mail to is getting too many emails too fast. Please contact the recipient using an alternative method.
Rate Limit	550	5.2.122	The recipient's server has denied your email. You’re sending mail to is getting too many emails too fast. Please contact the recipient using an alternative method.
Rate Limit	554	5.2.121	The recipient's server has denied your email. You’re sending mail to is getting too many emails too fast. Please contact the recipient using an alternative method.
Rate Limit	554	5.2.122	The recipient's server has denied your email. You’re sending mail to is getting too many emails too fast. Please contact the recipient using an alternative method.

---

Recipient Error

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	5.7.1	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	530	-	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. This usually happens when the recipient’s server refuses the connection or is unreachable for an extended period.
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. This usually happens when the recipient’s server refuses the connection or is unreachable for an extended period.
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	5.4.7	The email server has been trying to deliver the message for an extended period but has not been able to do so within the allowable time limit. The email has now been permanently rejected.
Recipient Error	550	5.5.5	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	5.7.105	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. This threshold could relate to various factors, such as the number of messages sent, the volume of inbound messages, or security thresholds based on suspicious activity.
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 method.
Recipient Error	550	5.7.999	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	5.8.2	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	551	-	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	552	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	553	5.0.0	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	553	5.1.8	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	554	4.3.5	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	554	5.1.0	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	554	5.1.2	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	554	5.2.0	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	554	5.4.6	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	554	5.5.4	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	554	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	554	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	555	5.7.1	The email platform you are trying to use is not supported for communication with Pixieset's systems. This error suggests that certain types of emails or configurations (e.g., unsupported email clients or formats) are not permitted by Pixieset's mail system.
Recipient Error	556	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	556	-	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	571	-	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	577	5.7.7	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	579	-	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	701	-	The recipient's server has denied your email. Communication outside their domain has been restricted. Please contact the recipient using an alternative method.

---

Rejection

Category	Code	Enhanced Code	Definition
Rejection	450	4.1.8	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	501	5.1.0	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	501	5.1.7	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	501	5.1.8	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	501	5.2.0	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	501	NA	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	533	5.7.1	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	550	5.1.0	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	550	5.1.0	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	550	5.1.7	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	550	5.1.8	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	550	5.2.3	The email message is too large for the recipient, exceeding their size limit.
Rejection	550	5.4.0	The email has been bounced back due to the email message exceeding the maximum number of allowed hops (transfers between mail servers). This usually happens when there is a mail loop or when the message has passed through too many servers.
Rejection	550	5.4.12	The email has been bounced back due to the email message exceeding the maximum number of allowed hops (transfers between mail servers). This usually happens when there is a mail loop or when the message has passed through too many servers.
Rejection	550	5.4.14	The email has been bounced back due to the email message exceeding the maximum number of allowed hops (transfers between mail servers). This usually happens when there is a mail loop or when the message has passed through too many servers.
Rejection	550	5.4.6	Your email was blocked by recepients email provider because mail loop detected.
Rejection	550	5.5.2	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	550	5.7.13	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	550	5.7.21	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	550	5.7.23	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	550	5.7.23	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	550	5.7.23	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	550	5.7.24	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	550	5.7.24	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	550	5.7.26	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	550	5.7.27	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	550	5.7.368	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	550	5.7.57	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	553	5.1.8	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	554	5.1.8	These errors indicate that the sending domain does not have valid DNS records. To resolve these issues, please ensure that the sending domain is verified and that the necessary DNS records are added with your DNS provider. Follow these instructions to resolve this issue.
Rejection	554	NA	Possible reasons: the right of the @ in the MAIL FROM does not appear to be valid or poor reputation of a sending domain.

---

Sender Reputation

How to Fix: Email Blocked for Potential Spam/Malicious Activity

1. Check IP and Domain Blacklists

• Use tools like: Blacklist Check

• If listed, follow the delisting procedure provided by the blacklist service.

2. Ensure Proper DNS Configuration

• SPF Record:

• DKIM (DomainKeys Identified Mail)

• DMARC (Domain-based Message Authentication, Reporting, and Conformance

Test DNS Records:

• MXToolbox for SPF/DKIM/DMARC record validation.

3. Monitor and Improve Email Reputation

• Microsoft SNDS: View the reputation of your IPs with Microsoft (Outlook, Hotmail).

  • Check at SNDS

• Google Postmaster Tools: Monitor how Gmail treats your emails.

  • Check at Postmaster Tools

4. Send Smaller Email Batches to Build Reputation

• Avoid sending a large volume of emails from a new or cold IP/domain. Start with a low volume and gradually increase to build trust.

5. Clean and Segment Email Lists

• Remove inactive or invalid addresses to reduce bounces.

• Use Email Validation tools to clean your lists before sending campaigns.

• Monitor complaints or spam reports to remove problematic recipients.

7. Check Email Content and Follow Best Practices

• Avoid spammy subject lines (e.g., "Congratulations!!!" or "Act Now!").

• Use a healthy image-to-text ratio (don't send only images).

• Ensure your links are safe and not blacklisted.

• Include an unsubscribe link in marketing emails to comply with anti-spam regulations.