What does Apple's CS02 error mean and how can I fix it on a shared IP?
Matthew Whittaker
Co-founder & CTO, Suped
Published 30 May 2025
Updated 19 Aug 2025
9 min read
Receiving a 554 5.7.1 [CS02] error when sending emails to Apple email addresses can be a frustrating experience, especially when you're using a shared IP address. This particular bounce message, 554 5.7.1 [CS02] Message rejected due to local policy., indicates that Apple's mail servers (like icloud.com, me.com, or mac.com) are rejecting your emails based on their internal policy filters. It's often a sign of a reputation issue related to the sending IP address, especially when it's shared among multiple senders.
While you might be diligently maintaining a clean email list and sending practices, the nature of shared IPs means that the sending behavior of other users on the same IP can impact your deliverability. If other senders on your shared IP are engaging in practices deemed undesirable by Apple, your legitimate emails can unfortunately get caught in the crossfire. Understanding what triggers this specific error is the first step toward effective troubleshooting and resolution.
Understanding Apple's CS02 error
The CS02 error code from Apple indicates that the email was rejected due to a local policy, which usually points to a poor sending reputation. Unlike other bounce codes that might indicate specific content issues or malformed addresses, CS02 often signifies that the sending IP or domain is flagged by Apple's internal systems as suspicious or associated with unwanted mail. This can be particularly challenging for senders on a shared IP, as their own sending habits might be impeccable, but the overall reputation of the shared IP pool affects their standing.
Apple, like other major mailbox providers, maintains sophisticated filtering mechanisms to protect its users from spam and phishing. These policies are dynamic and can be influenced by various factors, including spam complaints, engagement rates, and blocklist (or blacklist) appearances. When the CS02 error appears, it's Apple's way of saying, "We don't trust this source enough to deliver the message, based on our internal reputation assessment." It's crucial to differentiate this from other Apple errors, such as CS01, which also relates to local policy but can be triggered by different underlying issues, such as content or email forwarding practices.
A key aspect of this error on shared IPs is that you're inheriting the reputation of the entire pool. If an email service provider (ESP) manages a large pool of IPs and one or more users on that pool engage in spammy behavior, it can degrade the reputation for everyone. Even if you meticulously follow best practices, another sender's poor reputation can lead to your emails being rejected. This highlights the importance of working with an ESP that actively monitors and manages its shared IP reputation.
Diagnosing a CS02 error on a shared IP
When you encounter a CS02 error, the first step is to accurately diagnose the problem. Since it's a reputation-based block (or blacklist), you need to investigate the standing of your shared IP address. While direct access to Apple's internal reputation data is not available, several indicators can point to the issue. Checking public blocklists (or blacklists) is a good starting point, though not all blocks are publicly listed. Apple often uses its own internal metrics, which might not align perfectly with public lists.
The bounce message itself provides the crucial [CS02] code, confirming it's a specific Apple policy rejection. You can usually find the offending IP address within the full bounce message headers. Once you have the IP, you can use a blocklist checker to see if it's listed on any prominent public blocklists, which can indirectly affect Apple's perception of the IP. Keep in mind that getting blocklisted can severely impact your deliverability.
More importantly, open a dialogue with your ESP's support and compliance teams. They have access to more detailed logs and reputation data for their IPs. Since it's their shared IP, they are responsible for maintaining its health. Provide them with the full bounce message headers and the affected recipients so they can investigate internally and potentially address the issue with Apple or isolate the problematic sending behavior on their network. This proactive communication can greatly speed up the resolution process.
Factor
Impact on CS02
Action to check
IP reputation
Primary cause. Poor reputation due to other senders on the shared IP, or your own practices.
Resolving a CS02 error on a shared IP requires a multi-faceted approach, focusing on both your sending practices and collaboration with your ESP. Your primary action should be to ensure your own sending hygiene is impeccable. This means actively managing your email lists to remove inactive or problematic addresses, and segmenting your audience to ensure you're sending relevant content to engaged subscribers. Practices like troubleshooting Apple bounce errors often involve improving list quality.
Secondly, and critically, engage with your ESP's support team immediately. Since they own and manage the shared IP, they are best positioned to address the underlying reputation issue with Apple. Provide them with detailed information, including bounce logs and timestamps, so they can identify patterns or other senders contributing to the problem. They may need to contact Apple's postmasters directly to request delisting or provide assurances about their IP management practices. For example, if you are using Klaviyo, their compliance team would handle this.
While you wait for your ESP to resolve the IP reputation, consider temporarily adjusting your sending strategy to Apple domains. This might involve pausing campaigns to icloud.com, me.com, and mac.com addresses, or sending only to your most engaged Apple subscribers. This can help prevent further negative signals while the IP's reputation recovers. Also, ensure your email authentication records (SPF, DKIM, DMARC) are correctly configured for your domain, as this is a fundamental part of good sender reputation.
Best practices for shared IP sending
Maintain list hygiene: Regularly remove inactive, invalid, or bounced email addresses. This prevents hits on spam traps and reduces complaint rates.
Segment your audience: Send highly targeted content to engaged subscribers, especially for sensitive domains like Apple.
Monitor engagement: Track open and click rates and adjust your sending frequency or content based on subscriber behavior.
Comply with authentication: Ensure your SPF, DKIM, and DMARC records are correctly set up and aligned.
Preventing future CS02 issues
To prevent future CS02 errors and maintain strong deliverability on shared IPs, consistent monitoring and proactive measures are essential. Regularly use an email blocklist (blacklist) monitoring service to keep an eye on your sending IPs. While this won't directly show Apple's internal reputation, it can alert you to broader issues that might lead to CS02, like being listed on Cloudmark CSI-Global or Spamcop. A sudden appearance on a public blocklist can be an early warning sign of deteriorating IP health.
Beyond monitoring, cultivate an excellent sender reputation. This involves focusing on positive engagement, avoiding spam traps (which can lead to blacklisting), and adhering to best practices for email content and frequency. For Apple domains specifically, consistent positive interactions (opens, clicks) from Apple users can significantly improve your standing. Reviewing your email deliverability issues regularly is key.
Finally, assess whether a shared IP is still the right fit for your sending volume and reputation needs. While shared IPs are cost-effective and convenient, they inherently come with the risk of reputation fluctuations due to other users. If deliverability to critical domains like Apple is consistently a challenge, or your sending volume grows significantly, transitioning to a dedicated IP might be a worthwhile investment. This gives you full control over your IP's reputation, isolating you from the sending habits of others. However, dedicated IPs have their own challenges in terms of warming and maintenance.
Shared IP challenges
Reputation volatility: Deliverability is affected by the sending practices of all users on the same IP.
Limited control: Less direct control over IP warm-up and issue resolution processes.
Dependency on ESP: Heavily reliant on your ESP's proactive IP management and support.
Dedicated IP advantages
Full reputation control: Your deliverability reputation is solely based on your sending practices.
Predictable performance: More consistent inbox placement after proper warm-up, less affected by others.
Direct troubleshooting: Easier to diagnose and resolve IP-specific issues directly with mailbox providers.
Maintaining email deliverability
The Apple CS02 error is a clear signal that your email deliverability to Apple domains is being impacted by a reputation issue on your shared IP. While it can be frustrating to deal with problems caused by other senders, you have agency in how you respond. Focus on maintaining impeccable sending hygiene for your own campaigns, proactively communicating with your ESP, and continuously monitoring your sending reputation.
By understanding the nuances of shared IP reputation and the specific nature of Apple's local policies, you can take effective steps to mitigate the impact of CS02 errors. Remember that sustained effort in email deliverability best practices is crucial for long-term inbox success, especially when navigating the complexities of shared sending environments.
Views from the trenches
Best practices
Actively manage your subscriber list by regularly removing inactive or unengaged contacts.
Segment your email campaigns to send only to highly engaged users, especially for new or sensitive content.
Implement and maintain robust email authentication: SPF, DKIM, and DMARC records.
Common pitfalls
Ignoring bounce messages and not acting on them promptly can worsen IP reputation.
Not communicating with your ESP about deliverability issues, especially on shared IPs.
Sending emails to very old or unengaged lists, leading to spam traps and complaints.
Expert tips
If issues persist on a shared IP, inquire with your ESP about moving to a different, cleaner shared IP pool, or consider a dedicated IP if volume allows.
Build strong relationships with your ESP's support and compliance teams; they are your best allies in resolving shared IP issues.
Even if contacts open your emails, if those are machine opens (Apple MPP), they don't count towards positive engagement signals for reputation.
Expert view
Expert from Email Geeks says that the CS02 error is Apple's indication of a bad reputation, likely related to the sending IP.
2023-05-17 - Email Geeks
Expert view
Expert from Email Geeks suggests checking your IP on Cloudmark, as it's often part of Apple's filter stack, or messaging Apple postmasters for false positives.
Klaviyo, their compliance team would handle this.
Apple domains specifically, consistent positive interactions (opens, clicks) from Apple users can significantly improve your standing. Reviewing your email deliverability issues regularly is key.
