What causes Apple email bounces and how can I fix them?

Key findings

• Policy-based rejections: Errors like HM08 and CS02 specifically indicate that Apple's internal policies have led to the message rejection, rather than a non-existent mailbox.
• Sudden impact: These bounces can appear abruptly, affecting senders across both shared and dedicated IP addresses, despite prior good performance.
• No blocklist presence: Often, these issues occur even when sending IPs and domains are not listed on any public blocklists or blacklists, suggesting internal Apple mechanisms are at play.
• Content suspicion: If other technical checks pass, and other emails to Apple domains are accepted, the bounce is likely related to the specific content of the rejected email.
• Postmaster communication: While Apple Postmaster may not respond directly, reaching out is often recommended as internal action can resolve blocks without explicit notification.

Key considerations

• Thorough content review: Examine all elements of your email content, including text, images, and embedded URLs, particularly when comparing accepted and rejected messages.
• Engagement filtering: Continue to employ robust engagement filtering to maintain a healthy sender reputation, as this directly influences how Apple's filters perceive your mail.
• Monitor bounce types: Distinguish between soft bounces and hard bounces, and understand how your ESP classifies Apple rejections (e.g., ESPBLOCK) to manage your suppression lists accurately.
• Leverage tools: Use tools like aboutmy.email for general technical checks. For deeper insights into reputation, an email deliverability test can be invaluable.
• Contact support: If bounces persist, contacting Apple Postmaster remains a primary action, providing all relevant details, even if a direct reply is not guaranteed. More information on Apple's email server messages can be found on Apple Support's page.

Key opinions

• Sudden increase: Many marketers observe a significant, unexpected increase in Apple bounce rates, sometimes jumping from negligible to several percent in a short period.
• Content suspicion: When IPs are clear and other domains receive emails, marketers often suspect content as the root cause of Apple rejections.
• Postmaster unresponsiveness: A common complaint is the lack of direct response or acknowledgement from Apple's postmaster, adding to the difficulty of resolution.
• ESP classification: The way ESPs classify these Apple bounces (e.g., as ESPBLOCK versus BOUNCE) can impact whether contacts are automatically suppressed.
• Limited visibility: Even with diligent checks on blocklists and using tools like aboutmy.email, marketers may find no clear technical issues explaining the blocks.

Key considerations

• Detailed content analysis: Marketers should conduct a comprehensive review of all content elements, including linked URLs and image hosting URLs, when troubleshooting Apple bounces.
• Persistent outreach: Despite Apple Postmaster's inconsistent responses, consistent and polite communication is recommended, as issues can often be resolved without a direct reply.
• Adapt ESP handling: Understand your ESP's classification of Apple bounces to prevent incorrect subscriber suppression, which can impact future campaigns and deliverability.
• Engagement strategy: Double down on engagement filtering and list hygiene to proactively manage sender reputation.
• Anticipate unpredictability: Marketers should be prepared for the unpredictable nature of Apple's filtering and their postmaster's response patterns, requiring patience and a proactive approach to troubleshooting.

Key opinions

• Proofpoint involvement: Apple utilizes Proofpoint for filtering, making it a potential contact point for block resolution.
• Unpredictable responses: Apple Postmaster's responsiveness can vary greatly, from quick resolutions to no replies at all.
• Silent resolution: Despite a lack of direct communication, experts believe Apple will take appropriate action internally after receiving reports of deliverability issues.
• Privacy's role: Apple's significant privacy rules influence their filtering, contributing to a less transparent process.
• Content is key: If standard technical checks pass, experts often lean towards content as the likely cause for policy-based rejections.

Key considerations

• Leverage Proofpoint: If facing Apple blocks, contacting Proofpoint directly (via their IP check tool) can sometimes lead to quicker resolution.
• Detailed outreach: When contacting Apple Postmaster, provide clear, concise information about your sending practices, list acquisition, and measures taken to ensure compliance. More on this can be found in our guide on Apple policy-related bounces.
• Beyond blocklists: Understand that Apple's internal blocklists and filtering rules may not always align with public email blocklists, requiring a more nuanced diagnostic approach.
• Comprehensive content audit: Beyond visible content, scrutinize all URLs, image links, and tracking parameters, as these can trigger Apple's filters.
• Patience and persistence: Given Apple's often silent process, continued adherence to best practices and repeated, well-documented inquiries are crucial.

Key findings

• Hard bounces: These indicate permanent delivery failures, often due to invalid recipient addresses or unexpected sending errors.
• Soft bounces: These are temporary issues, such as a full inbox, an inactive mailbox, or a recipient server that is temporarily down.
• Policy rejections: Specific error messages like those from Apple (e.g., 5.7.1 [HM08]) explicitly state rejection due to local policy, pointing to a content or sender reputation issue.
• Spoofing concerns: Bounces can sometimes be a result of spammers spoofing your email address, causing undeliverable messages to bounce back to you.
• Bounce code significance: Each bounce error code carries specific information crucial for diagnosing the problem.

Key considerations

• List hygiene: Regularly clean your email lists to remove addresses that result in hard bounces, as persistent sending to these can damage your sender reputation. Our article why a valid email address hard bounced has more information.
• Server status: Verify the recipient's server status or any temporary issues, especially for soft bounces.
• Content compliance: Be aware that even legitimate content can trigger policy rejections if it aligns with patterns Apple's filters deem suspicious.
• Monitor specific errors: Pay close attention to the specific bounce error messages and refer to relevant documentation for precise troubleshooting steps. Learn more about bounce errors from Apple domains.
• Authentication: Ensure your emails are properly authenticated with SPF, DKIM, and DMARC to mitigate issues related to spoofing and improve trust.