Why are emails to Cox domains bouncing, and what are the updates on Cox email services?

Key findings

• Service transition: Cox has stopped directly hosting email services for @cox.net domains, with Yahoo Mail now handling these mailboxes. This means deliverability to Cox domains is now subject to Yahoo's email policies and filtering.
• Increased bounces: Mail sent to inactive or retired @cox.net addresses will result in hard bounces. These could include users who did not migrate their accounts to Yahoo or have since become inactive.
• Regional presence: Cox was a significant regional internet service provider (ISP) in the US, particularly in the South, meaning a notable portion of email lists may still contain @cox.net addresses.
• Phishing concerns: The transition period has also seen an increase in phishing scams targeting Cox email users, highlighting potential security vulnerabilities for older accounts.

Key considerations

• List hygiene: Regularly clean your email lists to remove bouncing Cox domain addresses. Continuing to send to these addresses can negatively impact your sender reputation.
• Monitoring bounces: Pay close attention to bounce codes from Yahoo Mail for @cox.net addresses to identify specific delivery issues.
• User awareness: Be aware that some users may have transferred their email service to Yahoo, while others might have abandoned their @cox.net accounts entirely. Consider re-engagement campaigns for these segments.
• Yahoo's policies: Understand that emails to former Cox domains are now subject to Yahoo's spam filtering and general email policies. This includes their approach to inactive accounts, which can result in bounces.

Key opinions

• Historical significance: Many marketers recall Cox as a long-standing, major US internet service provider with a substantial email user base, particularly in the southern US regions.
• New account policy: The cessation of new email account creation by Cox is seen as a clear signal that the number of active @cox.net addresses on mailing lists will naturally decline over time.
• Support for issues: A common concern is that Cox may be less responsive to deliverability issues, such as false positive rejections, now that email hosting is no longer a core service.
• Bounce implications: Marketers anticipate and are observing increased bounce rates as old or unmigrated Cox email addresses become permanently inactive.

Key considerations

• Proactive list cleaning: It is crucial for marketers to actively manage their email lists, removing hard bounces from @cox.net to preserve sender reputation and avoid being blocklisted.
• Bounce handling: Properly classifying and handling bounces from Cox/Yahoo domains is essential for maintaining a healthy sending infrastructure.
• Subscriber journey: Consider the possibility that subscribers with @cox.net addresses might have migrated to other email providers (e.g., Yahoo, Gmail) and adapt your acquisition and re-engagement strategies accordingly.
• Service retirement: Marketers should be prepared for the eventual retirement of legacy Cox domains, which could lead to automatic suppression of these addresses by email service providers (ESPs).

Key opinions

• Impact on smaller ISPs: Expert Steve589 from Email Geeks suggests that similar shifts from smaller ISPs can cause disproportionately large deliverability headaches, indicating that the Cox change is a blueprint for other potential service cutbacks.
• Authentication importance: EmailKarma, an expert from Email Geeks, advises that robust email authentication (SPF, DKIM, DMARC) is critical during ISP transitions to ensure mail is recognized as legitimate by the new handler (Yahoo).
• List decay: Wise_Laura from Email Geeks points out that email lists containing domains from ISPs that exit email hosting will naturally decay, emphasizing the unavoidable nature of list hygiene in such scenarios.
• Monitoring new policies: Marcel.beckers from Email Geeks highlights the necessity of monitoring new policies and bounce codes from the acquiring ISP (Yahoo) to understand why emails might be rejected.

Key considerations

• Adapt to Yahoo's rules: Senders must now adhere to Yahoo's deliverability best practices, including their handling of inactive accounts and spam filtering.
• Proactive list management: Regularly identify and remove defunct Cox addresses to prevent higher bounce rates, which can damage your sender reputation.
• Monitor delivery metrics: Keep a close eye on your bounce rates, complaint rates, and inbox placement for all domains, especially those previously managed by Cox, now handled by Yahoo.
• Consider old addresses: Experts from Spamresource often suggest that old addresses from discontinued services become spam traps over time, making it crucial to phase them out of active lists.

Key findings

• Service discontinuation: Cox Communications formally announced its decision to stop offering email hosting services directly, affecting all @cox.net email addresses.
• Yahoo migration: Existing @cox.net mailboxes were migrated to Yahoo Mail, which is now responsible for their operation and management, including spam filtering and bounce handling.
• No new accounts: The Cox Email Creation Policy explicitly states that new Cox email accounts can no longer be created, signaling a long-term decline in active @cox.net users.
• Error code availability: Cox provides a list of common email error codes on their support pages, which can help troubleshoot immediate delivery failures, although these may now be superseded by Yahoo's bounce codes.

Key considerations

• Adherence to new guidelines: Senders should consult Yahoo's postmaster guidelines and policies for optimal deliverability to @cox.net addresses.
• Bounce code interpretation: While Cox provides some error codes, the ultimate bounce responses for @cox.net are now determined by Yahoo's systems.
• Account activity policies: Understand that Yahoo has policies on inactive accounts, which can lead to addresses being deactivated and subsequent bounces.
• List decay management: Recognize that the population of active @cox.net email addresses will naturally shrink over time due to the cessation of new account creation and user migration.