What are the email deliverability impacts of Apple's Sign-in with Apple private relay service?
Matthew Whittaker
Co-founder & CTO, Suped
Published 25 Jul 2025
Updated 14 Aug 2025
10 min read
Summary
Apple's Sign-in with Apple service, especially its private relay feature, has introduced a new dynamic to email deliverability. This feature allows users to sign up for services with a unique, randomly generated email address (@privaterelay.appleid.com) that forwards messages to their actual email address. While designed to enhance user privacy, this system presents unique challenges for email senders. The primary concern revolves around the sender's inability to directly know the user's real email address and, crucially, when a user decides to disable email forwarding for that private relay address. This lack of transparency can lead to hidden deliverability issues and impact list hygiene.
Key findings
Masked addresses: Users are provided with unique, randomized email addresses (e.g., randomstring@privaterelay.appleid.com) that act as intermediaries, forwarding emails to their actual inbox. Senders never see the real address.
User control: Apple users retain significant control, allowing them to disable email forwarding from these private relay addresses at any time, often without direct notification to the sending party.
Silent failures: A critical issue is the potential for swallowed emails, where Apple may simply discard messages if forwarding is off, rather than returning a bounce notification to the sender. This makes it difficult to detect inactive addresses.
Sender registration: To ensure emails are delivered through the relay, senders must register their sending domains with Apple via their Apple Developer Portal.
Impact on metrics: While not directly tied to open rates (which are affected by Mail Privacy Protection), the private relay impacts the reliability of recipient lists and bounce handling, indirectly affecting overall campaign performance insights.
Key considerations
Robust bounce processing: Even with the risk of swallowed emails, prompt identification and removal of bounced addresses are crucial. Ensure your email service provider (ESP) or system accurately processes bounces.
Proactive list hygiene: Beyond bounces, consider implementing strategies for identifying and segmenting disengaged recipients from all types of email addresses, including private relay ones, to maintain a healthy list.
Domain registration: Verify that your sending domains are properly registered with Apple to ensure your emails are recognized and processed by the private relay service.
Authentication standards: Maintain strong email authentication (SPF, DKIM, DMARC) for all your sending domains. This foundational deliverability practice is essential for building and maintaining sender reputation across all recipients, including those using private relay.
Adaptation: Recognize that Apple's privacy features are part of a broader industry trend. Marketers should adapt by focusing on engagement metrics beyond opens and respecting user privacy choices.
What email marketers say
Email marketers have expressed a mix of concern and pragmatism regarding Apple's private relay service. While acknowledging the privacy benefits for users, the primary worry centers on the potential for reduced visibility into subscriber engagement and the difficulty of maintaining a clean email list when bounces may not be reliably returned. Many marketers are actively seeking strategies to adapt to this new paradigm, emphasizing the need for robust internal processes to track user engagement and identify inactive addresses.
Key opinions
Uncertainty of active addresses: A key concern is the inability to know definitively if a private relay address is still active and forwarding emails, as users can disable it at any time.
Reliance on bounces: Marketers typically rely on hard bounces to clean their lists. The possibility of swallowed emails (without a bounce notification) complicates this essential process.
Perceived deliverability dips: Some marketers have noted observed drops in deliverability for clients using Sign-in with Apple, suggesting a tangible impact.
Unforeseen challenges: While appearing similar to other aliases, Apple's approach to privacy could introduce unexpected complications for senders.
Limited early information: As a relatively new feature, initial information and guidance for marketers were scarce, leading to speculation and a learning curve.
Key considerations
Adapting list management: Marketers need to adapt their email list management strategies to account for the unique behavior of private relay addresses, moving beyond sole reliance on hard bounces.
Engagement tracking: Shifting focus to more reliable engagement metrics, such as clicks and conversions, becomes even more important to gauge subscriber interest and maintain domain reputation.
User experience focus: Prioritizing a positive user experience, including clear opt-out options, can mitigate issues from users disabling forwarding out of frustration.
Monitoring: Closely monitor deliverability rates and engagement for segments of your audience using Sign-in with Apple to identify any emerging patterns or issues. For example, Omeda emphasizes adapting strategies.
Marketer view
Marketer from Email Geeks asks if anyone has experienced deliverability issues with Apple's Sign-in with Apple. They are particularly concerned because users can technically remove themselves from receiving communication without the sender ever knowing, posing a unique challenge for email list management. This feature raises questions about how to maintain a clean and engaged subscriber base.
24 Oct 2019 - Email Geeks
Marketer view
Email marketer from Omeda states that Apple's Hide My Email feature impacts deliverability, necessitating adaptive marketing strategies. They suggest that while user privacy is enhanced, marketers must find new ways to measure engagement and ensure their emails still reach the intended inbox, moving away from reliance on traditional tracking methods.
15 Mar 2023 - Omeda
What the experts say
Email deliverability experts highlight that Apple's private relay addresses, while unique in their privacy-enhancing function, fundamentally behave like any other email alias from a purely technical standpoint. The key distinction, however, lies in Apple's handling of discarded emails, which can lead to a lack of bounce notifications. Experts stress the importance of understanding this specific behavior and implementing proactive testing and monitoring strategies to maintain a healthy sender reputation and ensure messages reach the inbox.
Key opinions
Alias functionality: Experts view private relay addresses primarily as email aliases tied to a user ID, similar to standard email forwarding setups.
No bounce for disabled forwarding: A significant expert observation is Apple's occasional practice of swallowing emails (i.e., not returning a bounce) when a user has turned off forwarding for their private relay address. This is a crucial difference from typical email behavior.
Sender domain registration: It is confirmed that app developers must register their sending domains with Apple to ensure emails are correctly routed through the private relay service.
Importance of testing: Due to Apple's unique behaviors and potential for silent failures, proactive testing of deliverability to private relay addresses is strongly advised.
Predictable address pattern: The private relay addresses consistently follow the pattern of a unique alphanumeric string followed by @privaterelay.appleid.com.
Key considerations
Enhanced monitoring: Beyond traditional bounce tracking, senders should implement advanced monitoring to detect potential silent failures and maintain high deliverability, possibly using engagement data like clicks to infer list health.
Compliance with Apple's guidelines: Ensure your email infrastructure and practices align with Apple's specific requirements for sending through the private relay.
Proactive list cleaning: Given the risk of silent failures, adopt more proactive list hygiene practices, such as sunsetting non-engaging subscribers or employing re-engagement campaigns for segments likely to use private relay addresses. This complements strategies for dealing with blocklist impacts.
Authentication best practices: Reinforce adherence to SPF, DKIM, and DMARC. Strong authentication is fundamental for any email program, particularly when dealing with intermediaries like private relay. For example, proper configuration of these records is vital.
Ongoing education: Stay informed about updates from Apple and the broader email industry regarding privacy features, as policies and behaviors may evolve.
Expert view
Expert from Email Geeks advises that the app developer must log in with their Apple ID and register the domain used for sending to these private relay addresses. This step is critical for Apple to recognize and properly route emails through their privacy-focused system, ensuring delivery to the intended recipients.
24 Oct 2019 - Email Geeks
Expert view
Deliverability expert from Spamresource indicates that services like Apple Private Relay underscore the growing importance of strong authentication measures like DMARC for email deliverability. They highlight that verifying sender identity becomes even more critical when an intermediary service is involved, ensuring trust and reducing spam.
10 Mar 2024 - Spamresource
What the documentation says
Apple's official documentation and related technical resources clarify the purpose and operational requirements of the private email relay service. The primary emphasis is on user privacy and control, with mechanisms in place to allow users to manage their communication preferences. For senders, the documentation outlines specific steps, such as domain registration, that are necessary to ensure successful email delivery through these privacy-enhancing aliases.
Key findings
Mandatory domain registration: Apple explicitly requires app developers to register their sending domains with Apple to use the private email relay service for communicating with users who sign in with Apple.
Privacy by design: The service is fundamentally designed to enhance user privacy by masking their real email addresses and preventing tracking pixels.
User control over forwarding: Users have direct control within their Apple ID settings to enable or disable email forwarding from a generated private relay address to their real inbox.
Unique alias generation: Each private relay email address is a unique, randomly generated alias, ensuring that a user's true email address is never exposed to the third-party service.
No unique identifiers collected: Documentation from sources like WIRED confirms that the service does not collect unique identifiers or information about the user's identity or location, reinforcing the privacy aspect.
Key considerations
Adherence to Apple's API: Developers must integrate with Apple's Sign-in with Apple API to correctly obtain and communicate with private relay addresses.
Impact on email tracking: While Private Relay specifically handles email forwarding, it's part of a broader privacy initiative (Mail Privacy Protection) that blocks IP address and open tracking, requiring marketers to rethink how they measure engagement.
User privacy paramount: Documentation consistently emphasizes that the user's privacy choices should be respected. This includes promptly stopping emails if a user disables forwarding, even if a bounce isn't immediately received.
Authentication standards: Proper email authentication (SPF, DKIM, DMARC) is assumed and remains critical for emails to be trusted by Apple's relay service. Reviewing your DMARC reports for private relay domains is recommended.
Technical article
Apple Developer documentation explains that app developers need to log in with their Apple ID and register the domains that will be sending emails to these private relay addresses. This registration process is a foundational step, ensuring that only authorized senders can communicate with users through the privacy relay, maintaining the integrity of the service.
15 Oct 2019 - Apple Developer
Technical article
Maileroo documentation describes Apple's Private Relay email system as a privacy-enhancing feature that masks real email addresses for users. They elaborate that this system generates unique, disposable email addresses, providing an essential layer of anonymity and control for individuals when signing up for online services.
