Common email bounce messages
This article explains the meaning of common email bounce messages, categorized by their SMTP error code, and provides solutions for resolving them.
If you cannot find your particular bounce message here, refer to the mail provider for an interpretation of their message.
For a video tutorial see Email Help - Bounce Messages.
Error Code Classification
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4xx bounce - A 400 error indicates a temporary failure, which means that a temporary condition has caused the email to not be delivered. The error can likely be resolved by sending the email again at a later time.
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5xx bounce - A 500 error indicates a permanent failure. This error does not mean you will never be able to send email again; you must change some aspect of either the message or the method of delivery for email to successfully be delivered. The bounce message should indicate what needs to change.
Note: If Rackspace bounced your email message, the generating server should show emailsrvr.com in the bounce message. If you do not see emailsrvr.com in the bounce message, the recipient’s provider might have blocked the message.
SMTP error | Explanation | Solution |
|---|---|---|
Host or domain name not found. MX host not found. | There are no MX records for the recipient's domain | This message will not deliver. The recipient must create MX records at their DNS host so that they can receive email. More information on MX records. |
| The recipient cannot verify the existence of your domain. | Verify that your domain’s DNS is properly configured. See Set up DNS records for instructions. |
| The recipient’s server has received too much spam from this source. | Try sending the message again later. Follow the steps in Best practices for sending person-to-person email or Best practices for sending emails to many recipients to avoid having your email marked as spam. Ask the recipient to safelist or whitelist your domain. |
| An intermittent issue has occurred. | Wait and send the message again at a later time. |
| The sending IP address has too many concurrent connections with our servers. | Reduce concurrent connections to our servers to five or less, and then send again. |
| Your domain has split domain routing enabled, and the recipient's address (hosted on the external mail server) soft fails. | The message is deferred to be resent at a later time. Ensure that the external mail server is running and accepting connections over port 25 (SMTP). |
| The domain from which you are sending is not valid. | You must use a valid domain for sending email. |
| The content of this message has been deemed spam by the internet community | Spam definitions change rapidly. However, there are measures you can take to prevent having your message rejected as spam. See Best practices for sending person-to-person email or Best practices for sending emails to many recipients. |
| Your domain exists in Rackspace, but the full email address you sent from does not. | Create the address in the form of a mailbox, list, or alias to send mail from Rackspace Cloud Office. |
| The recipient's email address does not exist in the Rackspace hosted domain. | Add the email address to Rackspace hosted domain. |
| The message size exceeds the maximum message size allowed by our servers (50 MB). | Ensure that the message size is under the allowed threshold and resend the message. |
| The message contains an attachment file type on the blocked list. | Remove the blocked file type and re send. |
| The message contains an attachment file type on Outlook's blocked list. | Remove the blocked file type and resend. |
| The message contains an attachment that can be used to exploit WinZip associated files: .b64, .bhx, .hqx, .mim, .uue?, or .xxe | Remove the banned file type and resend. |
| The recipient's address does not exist, or the recipient domain's DNS configuration has an issue. | Check the recipient address for any misspellings or typos. Resend the message. If the recipient is hosted at Rackspace Cloud Office, have them verify that their DNS is properly configured to receive mail. |
| The sending IP address is blocked internally. | Safelist the IP address, the sending domain or address, or both. |
| The sending server is Blocklisted by the Spamhaus PBL. | The sender must follow the https://www.spamhaus.org/lookup/ link to request remediation from the Spamhaus Blocklist. Safelisting the sender will not allow an exception. The only solution is for the sender to get the IP address removed from the Spamhaus list. |
| The sending server is Blocklisted by Cloudmark. | The sender must follow the https://csi.cloudmark.com/reset-request link to request remediation from the Cloudmark Blocklist. The recipient can safelist the sender in the meantime. |
| The sending server is Blocklisted by Senderscore. | The sender must follow the https://senderscore.org/rtbl/ link to request remediation from Senderscore's Blocklist. The recipient can safelist the sender in the meantime. |
| The sending server is Blocklisted by the Spamhaus XBL. | The sender must follow the https://www.spamhaus.org/lookup/ link to request remediation from the Spamhaus Blocklist. The recipient can safelist the sender in the meantime. |
| The sending server is Blocklisted by the Spamhaus SBL. | The sender must follow the https://www.spamhaus.org/lookup/ link to request remediation from the Spamhaus Blocklist. The recipient can safelist the sender in the meantime. |
| The sending server is Blocklisted by Spamcop. | The sender must follow the https://spamcop.net/bl.shtml link to learn more about Spamcop's Blocklist. If Spamcop receives no other spam reports from that IP address within 24 hours, the IP address is removed. The recipient can safelist the sender in the meantime. |
| The sender is Blocklisted at the domain level. | Remove the sender from the domain level Blocklist or safelist at the recipient level. |
| The sender is Blocklisted at the user level. | Remove the sender from the user level Blocklist. |
| The name of the attached document is longer than 50 characters. | Shorten the name of the document that you are sending, and resend. |
| The domain has split domain routing enabled, and the recipient's address (hosted on the external mail server) permanently fails. | Confirm that the recipient's address exists on the external server (check for misspellings) and resend the message. |
| The recipient's address (and domain) does not exist on our system. | Check the recipient's address for any potential misspellings or typos, and then resend the message. |
| The recipient's address (and domain) does not exist on our system. | Check the recipient's address for any potential misspellings or typos, and then resend the message. |
| The sender failed the DMARC policy, and the policy is set to reject. | Verify the sending source and ensure that it is compliant with the DMARC policy. It might also be necessary for the sender to update their DMARC DNS record. The sender must resend the message. For more information, see DNS record definitions. |
| The sender failed the SPF policy, and the policy is set to reject. | Verify the sending source and ensure that it is compliant with the SPF policy. For more information, see DNS record definitions |
Updated about 18 hours ago