What does Apple's CS02 error mean and how can I fix it on a shared IP?

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.

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.

Email marketer from Mailjet shares that to resolve CS02 errors, focus on improving overall email health. This includes segmenting your lists to send targeted content, removing unengaged subscribers, and monitoring feedback loops to address complaints promptly. Building a positive sending reputation will help overcome shared IP challenges.

Email marketer from Email Marketing Forum highlights that shared IP addresses can be problematic if other users are engaging in spammy behavior. To address CS02 errors, actively monitor your IP reputation and consider switching to a dedicated IP if problems persist, giving you more control over your sending reputation.

Email marketer from GlockApps shares that you should use monitoring tools to track your email deliverability rates across various ISPs, including Apple. These tools provide insights into inbox placement, spam folder delivery, and potential deliverability issues that may cause CS02 errors.

Marketer from Email Geeks confirms that the issue is a policy block based on IP reputation. Also mentions that Klaviyo uses Sendgrid's sending infrastructure.

Email marketer from Litmus suggests checking if your IP address is on any email blocklists. If you find yourself on a blocklist, take steps to get removed by following the blocklist's removal process. This can significantly improve your email deliverability and reduce CS02 errors.

Email marketer from SendPulse shares the importance of warming up your IP address gradually when starting with a new shared IP. This involves sending small volumes initially and gradually increasing them over time. This helps establish a positive sending reputation with ISPs and reduces the likelihood of being blocked.

Email marketer from Constant Contact emphasizes the importance of setting up email authentication protocols (SPF, DKIM, and DMARC). These protocols help verify that you are authorized to send emails on behalf of your domain, improving deliverability and reducing the risk of being flagged as spam.

Expert from Email Geeks explains that Apple's CS02 error message means the sender has a bad reputation.

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.

Expert from Word to the Wise explains that being on shared IPs require constant monitoring because you're affected by neighbors. To mitigate negative reputation impacts, closely monitor your metrics, comply with email standards, and warm up your IP correctly to avoid blocks like CS02.

Expert from Spamresource shares that bounce codes like 554 5.7.1 are often used to signify policy issues, including reputation-based blocks. Shared IP addresses are commonly affected because the actions of other users can negatively impact your sending reputation. Addressing this involves cleaning your list and improving sender authentication.

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.

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.

Documentation from Google Postmaster Tools advises regularly monitoring your sender reputation using their tools. Even though it’s for Google, it gives an overall idea of your sending reputation. Low reputation scores indicate potential deliverability issues, including blocks from other providers like Apple.

Documentation from SparkPost explains that sending from a shared IP means your reputation is linked to other senders using the same IP. Therefore, it's crucial to maintain high email quality, monitor bounce rates, and promptly address any deliverability issues reported by recipients or ISPs like Apple. Contacting Apple postmaster is advised.