Summary
Apple's CS02 error indicates a policy-based block due to a poor IP reputation, often triggered when using a shared IP address where the sending behavior of other users can negatively affect your deliverability. Addressing this issue requires a comprehensive strategy, including contacting your ESP for support, implementing robust email authentication (SPF, DKIM, DMARC), consistently monitoring your sending reputation and deliverability metrics using tools like Google Postmaster Tools, proactively cleaning your email lists, warming up IP addresses gradually, adhering to email sending best practices, promptly handling feedback loops and complaints, and considering switching to a dedicated IP if the problems continue. In certain situations, it may be beneficial to request whitelisting from Apple.
Key findings
- Reputation Indicator: The CS02 error signifies a problem with your sending IP's reputation, leading to a policy-based block.
- Shared IP Risks: Shared IP addresses are vulnerable to negative reputation impacts caused by the actions of other users on the same IP.
- Authentication Importance: Proper email authentication protocols (SPF, DKIM, DMARC) are essential for verifying sender legitimacy and improving deliverability.
- Proactive Monitoring: Regular monitoring of your sending reputation, deliverability rates, and blocklist status is crucial for identifying and addressing issues promptly.
Key considerations
- ESP Support: Reach out to your Email Service Provider (ESP) for assistance in resolving the IP reputation issue and implementing necessary fixes.
- List Management: Maintain a clean and engaged email list by regularly removing inactive or problematic subscribers.
- Gradual Warm-up: Gradually warm up new IP addresses, especially when starting with a shared IP, to establish a positive sending reputation.
- Feedback Loops: Actively monitor and address feedback loops and complaints to improve sender reputation and mitigate deliverability issues.
- Dedicated IP Option: Consider switching to a dedicated IP address for greater control over your sending reputation if problems persist on a shared IP.
- Apple Whitelisting: If you believe your emails are being incorrectly blocked, consider requesting whitelisting from Apple.
What email marketers say
9 marketer opinions
Apple's CS02 error indicates a policy-based block due to poor IP reputation, often exacerbated by using a shared IP. Resolving this requires a multi-faceted approach, including monitoring sender reputation, improving email authentication (SPF, DKIM, DMARC), cleaning email lists, warming up IP addresses gradually, and actively addressing complaints and feedback loops. If issues persist, switching to a dedicated IP may be necessary.
Key opinions
- Reputation Impact: Shared IPs are affected by the sending behavior of all users on the IP, impacting deliverability.
- Email Authentication: Proper email authentication (SPF, DKIM, DMARC) is critical for verifying sender legitimacy.
- List Hygiene: Cleaning email lists and removing unengaged subscribers improves sender reputation.
- Monitoring Tools: Tools are available to monitor IP reputation, blocklist status, and deliverability rates.
Key considerations
- Gradual Warm-up: Gradually warm up your IP address when starting with a new shared IP to establish a positive reputation.
- Feedback Loops: Monitor and address feedback loops and complaints promptly to maintain a good sender reputation.
- Dedicated IP: If issues persist on a shared IP, consider switching to a dedicated IP for greater control over reputation.
- Contact Apple: If incorrectly blocked, request whitelisting from Apple.
Marketer view
Email marketer from EmailOctopus shares that when using a shared IP, your sender reputation is influenced by other users on the same IP. To mitigate CS02 errors, monitor your sending practices, authenticate your emails (SPF, DKIM, DMARC), and request whitelisting from Apple if you believe your emails are being incorrectly blocked.
24 Apr 2025 - EmailOctopus
Marketer view
Email marketer from Reddit advises checking your sending domain's reputation using online tools. If the reputation is poor, especially due to being on a shared IP, work on improving it by cleaning your email lists, authenticating your emails, and sending consistently high-quality content.
17 Feb 2022 - Reddit
What the experts say
4 expert opinions
Apple's CS02 error signifies a policy-based block stemming from a bad IP reputation, often affecting senders using shared IPs due to the actions of other users. Resolving the issue involves contacting the ESP for support, cleaning email lists, improving sender authentication, closely monitoring sending metrics, complying with email standards, and correctly warming up the IP.
Key opinions
- Reputation Based: CS02 indicates a problem with your sending IP's reputation.
- Shared IP Risk: Shared IP addresses are susceptible to negative reputation impacts from other users.
- ESP Responsibility: ESPs have a responsibility to maintain the reputation of their shared IPs.
Key considerations
- Contact ESP: Reach out to your ESP for support in addressing the IP reputation issue.
- List Cleaning: Regularly clean your email list to remove inactive or problematic subscribers.
- Authentication: Implement and maintain proper email authentication protocols (SPF, DKIM, DMARC).
- Monitoring: Closely monitor your sending metrics (bounce rates, complaints) to identify and address potential issues proactively.
- Compliance: Comply with email sending standards and best practices to maintain a good sending reputation.
- IP Warmup: Warm up the IP address correctly, especially when starting with a new IP or after a period of inactivity.
Expert view
Expert from Email Geeks explains that Apple's CS02 error message means the sender has a bad reputation.
12 Feb 2025 - Email Geeks
Expert view
Expert from Email Geeks suggests that since the sender is on a shared IP and not doing anything wrong, they should push on their ESP support to fix the IP reputation issue.
3 Mar 2022 - Email Geeks
What the documentation says
4 technical articles
The CS02 error from Apple signifies a policy-related rejection due to poor IP reputation, often linked to shared IPs where your reputation is affected by other senders. Resolving this necessitates maintaining high email quality, monitoring bounce rates and sender reputation using tools like Google Postmaster Tools, addressing deliverability issues, authenticating emails (SPF, DKIM, DMARC), and adhering to general email sending best practices. Contacting Apple's postmaster may also be necessary.
Key findings
- Policy Rejection: CS02 indicates a policy rejection, specifically related to IP reputation.
- Shared IP Impact: Sending from a shared IP links your reputation to other senders on that IP.
- Reputation Monitoring: Tools like Google Postmaster Tools can provide insights into your sender reputation.
Key considerations
- Email Quality: Maintain high email quality to prevent deliverability issues.
- Bounce Rate: Monitor bounce rates to identify and address deliverability problems.
- Authentication: Ensure proper email authentication (SPF, DKIM, DMARC) to improve deliverability.
- Best Practices: Adhere to email sending best practices to maintain a good reputation.
- Contact Apple: Contact Apple's postmaster for assistance with deliverability issues.
Technical article
Documentation from Apple Support explains that the 554 5.7.1 error in email bounce messages generally indicates a policy-related rejection. The 'CS02' code specifically points to issues related to IP address reputation or sending policies, often triggered when sending from a shared IP address with poor reputation.
16 Aug 2024 - Apple Support
Technical article
Documentation from Microsoft details that while the CS02 error is specific to Apple, similar errors across different providers often stem from IP reputation. Improving sender reputation involves ensuring proper authentication (SPF, DKIM, DMARC), maintaining low complaint rates, and adhering to email sending best practices.
22 Feb 2024 - Microsoft Support
Can I use DMARC with shared IP addresses?
Do I need an IP warm-up when moving to a new ESP with shared IPs?
How can I improve email deliverability on a shared IP for marketing automation emails like abandoned carts?
How do shared IP pools and sending domains impact email sender reputation for ESPs?
What causes Apple's policy-related (CS01) bounce messages and how can I resolve them?
What is a shared IP address and how does it affect email deliverability?
