Why are cox.net email addresses soft bouncing and showing bounce errors?

Key findings

• Sudden spikes: An unusually high soft bounce rate for Cox.net addresses has been observed by multiple senders, often appearing without clear immediate cause.
• Temporary server issues: Soft bounces are typically transient, indicating temporary problems like a full mailbox, oversized messages, or the recipient's server being temporarily unavailable. See more about how email service providers manage soft bounces.
• Distinguishing errors: Some reported errors, such as '550 5.1.1 <*> Recipient address rejected: User does not exist,' might appear as hard bounces but could potentially be false positives during periods of Cox.net system instability.
• Systemic issues: Suspected underlying issues at Cox (like LDAP problems) can lead to widespread, short-term deliverability challenges, including increased delays and bounces. More on this can be found in our article on why emails to Cox domains are bouncing.

Key considerations

• Monitor bounce types: While soft bounces are temporary, a sudden increase or the presence of hard bounce codes ('550' errors) requires closer inspection. Understand the difference between soft bounces and hard bounces.
• Historical data: Consider if high bounce rates or delays to Cox.net are a new phenomenon or a recurring issue, as this can indicate different underlying problems.
• Temporary vs. permanent: Be cautious before marking users as permanently undeliverable based on 'user does not exist' errors during periods of suspected ISP instability, especially if they've had recent engagement.
• Direct communication: In cases of widespread and persistent issues, contacting Cox.net postmaster directly with specific examples (sending IPs, error messages, timestamps) can help in diagnosis and resolution.

Key opinions

• Recent increase: Many marketers report seeing an increase in soft bounces specifically for Cox.net addresses over recent weeks or days, indicating a shift in Cox's handling of incoming mail.
• Block bouncing: Some observe frequent blocklist bounces, suggesting that Cox.net might be employing stricter filtering or that sender IPs are getting blocklisted more often. Understanding what happens when your domain is on a blacklist is crucial.
• Delays are common: Delays have always been a more prevalent issue with Cox.net, but recent observations suggest these delays have become even more pronounced alongside increased bounce rates.
• False hard bounces: There's a concern that some 'user does not exist' bounces (typically hard bounces) might be false during periods of Cox.net instability, especially for recently engaged contacts. This is similar to why a valid email address might hard bounce.

Key considerations

• List segmentation: Identify what percentage of your list is composed of Cox.net addresses to gauge the impact of these issues on overall campaign performance.
• Bounce analysis: Carefully analyze bounce logs and codes to differentiate between true soft bounces (temporary issues) and potentially misleading hard bounces during problematic periods. Further information on this can be found at Twilio's bounce management guide.
• Engagement tracking: If 'user does not exist' errors occur for engaged subscribers, consider a cautious re-try or a different engagement channel before removing them from your list permanently.
• Monitoring deliverability: Implement robust deliverability monitoring to quickly identify anomalies specific to certain ISPs, like Cox.net, allowing for faster response and mitigation.

Key opinions

• Widespread reports: Experts confirm that others have been reporting similar issues with Cox.net in recent days, suggesting a broader problem rather than isolated incidents specific to one sender.
• LDAP issues: Some experts point to underlying LDAP (Lightweight Directory Access Protocol) issues at Cox as a potential cause for the increased soft bounces and delivery problems. This can impact the overall email deliverability rate.
• Misleading 4xx/5xx errors: While some messages might show 4xx (temporary) errors, or even 550 (permanent) errors, many emails might still be delivered successfully despite the bounce reports, indicating potential miscategorization by the receiving server during outages.
• Unclear root cause: Despite ongoing observations, the precise root cause of the current Cox.net issues is not always immediately clear, requiring deeper investigation from the ISP side. Our guide on how to resolve email deliverability issues with Cox.net offers more insights.

Key considerations

• Data for diagnosis: To properly diagnose ongoing issues, experts suggest providing specific data points like sending IPs, exact error messages, and approximate time windows of the incidents.
• False 550s: Be aware that 550 errors, typically indicating permanent failures, might be temporarily misleading if an ISP is experiencing system-wide issues, even for addresses with recent engagement.
• Trusted channels: Engaging directly with ISP postmasters or their designated contacts through trusted channels can expedite the troubleshooting process for significant deliverability disruptions.
• Cautious list cleaning: Avoid immediate removal of email addresses based on temporary or potentially false bounce indicators during periods of ISP instability. Aggressive list cleaning practices can sometimes remove valid subscribers.

Key findings

• Soft bounce definition: Documentation confirms that a soft bounce is a temporary delivery failure, meaning the email server successfully received the message but could not deliver it to the inbox at that moment.
• Common soft bounce causes: Standard reasons for soft bounces include a full recipient mailbox, the message being too large, or a temporary server outage or busy state at the receiving end.
• Resend attempts: Email services are designed to automatically retry sending messages that result in a soft bounce over a period of time, as the issue is expected to be transient. This is part of standard technical solutions for deliverability.
• Hard bounce vs. soft bounce: It is critical to distinguish soft bounces from hard bounces, which indicate a permanent failure (e.g., recipient address does not exist), as documented in email bounce management best practices.

Key considerations

• Error code interpretation: Refer to standard SMTP (Simple Mail Transfer Protocol) error codes (e.g., 4xx for temporary failures, 5xx for permanent failures) to accurately interpret bounce messages, even if an ISP is experiencing unique issues.
• ISP-specific nuances: While general definitions apply, ISPs may have specific internal policies or error responses that complicate standard interpretation during system outages or maintenance. Understanding why emails fail can help.
• Server communication: A server rejecting an email temporarily (soft bounce) means it has communicated its inability to deliver for a fleeting reason, prompting the sending server to queue the message for later attempts.
• No retrieval of bounced messages: Once an email bounces, it does not reside on the receiving server and cannot be retrieved, underscoring the importance of addressing underlying deliverability problems.