How does Apple Private Relay encode email addresses and how does domain whitelisting affect deliverability?
Michael Ko
Co-founder & CEO, Suped
Published 3 Jun 2025
Updated 17 Aug 2025
8 min read
Apple Private Relay is a privacy feature designed to give users more control over their online identity. When enabled, it masks a user's IP address and generates unique, anonymous email addresses for signing up for services or newsletters. These iCloud Private Relay addresses act as intermediaries, forwarding emails to the user's real inbox without revealing their actual email address to the sender. This adds a significant layer of privacy, but it also introduces complexities for email senders trying to ensure deliverability.
One common concern for email marketers and transactional senders is understanding how these addresses are encoded and, crucially, how domain whitelisting affects whether their emails reach the intended recipients. Without proper configuration, emails sent to Private Relay addresses can face significant deliverability issues, often leading to bounces or messages landing in spam folders.
Navigating Apple's privacy features requires a clear understanding of the technical mechanisms at play. We’ll explore the structure of these unique email addresses and delve into the critical role of domain whitelisting in maintaining your email deliverability with Apple's Private Relay service.
How Apple Private Relay encodes email addresses
When an Apple user opts to hide their email with a service like Sign In with Apple, Private Relay generates a unique, random email address. These addresses typically follow a pattern like unique-alphanumeric-string@privaterelay.appleid.com. The key part here is @privaterelay.appleid.com, which signifies that the email is being routed through Apple's relay service.
The unique-alphanumeric-string in the local part of the address contains encrypted information that allows Apple to map it back to the user's actual email address. This encoding is dynamic and ensures that if a user decides to stop receiving emails from a particular sender, they can simply disable that specific relay address without affecting their primary email. From the sender's perspective, they only see this generated address, preserving the user's privacy.
It’s important to note that while the email address is masked, the From name (e.g., Your Company Name) that you configure for your emails will still be displayed to the recipient. This helps maintain brand recognition even though the underlying email address is privatized. The encoding serves solely as a privacy layer, not a full obfuscation of the sender's identity or brand.
Example of an Apple Private Relay Email Address
unique-string@privaterelay.appleid.com
The necessity of domain whitelisting
To successfully send emails to @privaterelay.appleid.com addresses, your sending domain needs to be whitelisted (or registered) with Apple. This is a crucial step for any sender, especially those utilizing Sign In with Apple. If your domain isn't whitelisted, emails will likely soft bounce with errors like 'domain not found' or '5.7.1 Email rejected due to transformation error'.
The whitelisting process typically involves your Apple app developers. They need to configure your application's capabilities to enable the Private Email Relay service and add your sending domains to your Apple Developer Account. This establishes a trusted connection between your domain and Apple's relay service, allowing legitimate emails to pass through.
Even if you're sending from your own domain through an Email Service Provider (ESP), this whitelisting is still necessary. Your ESP simply handles the technical sending, but the permission to send to Apple's relay addresses comes from your domain's registration with Apple. Ensure your ESP can provide custom return paths that align with your whitelisted domain for optimal deliverability.
Unwhitelisted domain
Email flow: Emails sent to Private Relay addresses are blocked at Apple's servers.
Deliverability: Messages will hard bounce or soft bounce, resulting in zero delivery to these recipients.
Reputation: Repeated bounces can negatively impact your sender reputation with other mailbox providers.
Whitelisted domain
Email flow: Emails are accepted by Apple's servers and relayed to the user's real inbox.
Deliverability: High likelihood of successful delivery to Private Relay users.
Reputation: Maintains a good sender reputation and improves inbox placement.
For detailed instructions on registering your domains, you can refer to the Apple Developer documentation. It's a critical step in ensuring your emails can successfully reach users who opt for this privacy feature.
Impact on email deliverability
Apple Private Relay has a direct impact on email deliverability, primarily through its interaction with sender authentication and bounce management. Beyond the simple act of whitelisting, you need to ensure your email authentication protocols like SPF, DKIM, and DMARC are correctly configured. Apple heavily relies on these checks to determine the legitimacy of incoming mail.
If your mail fails DMARC checks, Apple is more likely to reject it, leading to non-delivery. This is a common reason why emails sent through Private Relay might go to spam or soft bounce. Monitoring your DMARC reports becomes even more critical when sending to these addresses, as it provides visibility into authentication failures.
Furthermore, Apple's Mail Privacy Protection (MPP), which is often used in conjunction with Private Relay, impacts how open rates are tracked. MPP pre-fetches email content, making it appear as if an email has been opened, even if the user hasn't seen it yet. This can inflate your reported open rates, making it harder to accurately gauge engagement for IP warmup strategy and open rate tracking.
While Private Relay enhances user privacy, it can create a 'black box' effect for senders regarding bounce management. When you encounter soft bounces from @privaterelay.appleid.com addresses, it's often a sign that your domain is not properly whitelisted or that there are authentication issues. Resolving these requires verifying your Apple developer account settings and ensuring your email infrastructure meets Apple's requirements.
Handling private relay addresses for senders
Managing email lists that include Apple Private Relay addresses requires a proactive approach to maintain good sender reputation and ensure high deliverability rates. First and foremost, verify that your domain is correctly whitelisted with Apple. This is foundational. If you're encountering persistent bounces, this should be your first point of investigation.
Next, pay close attention to your email authentication. Strong SPF, DKIM, and DMARC configurations are not just best practices, but necessities for Apple to trust your emails. Regularly check your DMARC reports for any authentication failures or suspected spam temp fails that could indicate underlying issues affecting your sender reputation.
While you cannot directly see a user's real email address when they use Private Relay, you can still monitor engagement metrics beyond opens, such as clicks and conversions, to understand how these recipients interact with your content. It's crucial to handle Private Relay addresses appropriately and not treat them as suspicious, provided your domain is whitelisted.
Some ESPs may state that they do not support Private Relay. This might mean they don't have built-in features to manage the whitelisting process for you, or they have limitations with custom return paths. Always clarify these points with your provider. Ultimately, the responsibility for whitelisting and ensuring proper authentication lies with the sender's domain configuration.
Navigating private relay for better deliverability
Understanding Apple Private Relay is crucial for anyone involved in email deliverability. These anonymized email addresses are designed to protect user privacy by acting as a proxy between your sending system and the user's real inbox. The encoding process involves generating a unique, random string that maps to the user’s actual email, all under the @privaterelay.appleid.com domain.
The key to successful deliverability to these addresses lies in domain whitelisting with Apple. Without this critical step, your emails will likely bounce, impacting your sender reputation and overall deliverability. This whitelisting typically falls to your Apple app developers to configure within your Apple Developer Account, linking your sending domain to the Private Email Relay service.
Beyond whitelisting, maintaining robust email authentication protocols—SPF, DKIM, and DMARC—is essential. Apple rigorously checks these to ensure email legitimacy. By addressing these technical requirements and monitoring your email performance closely, you can navigate the complexities of Apple Private Relay and continue to reach your audience effectively while respecting user privacy.
Views from the trenches
Best practices
Ensure your sending domain is properly registered and whitelisted with Apple via your developer account.
Maintain strong SPF, DKIM, and DMARC authentication records to meet Apple's strict requirements.
Regularly monitor DMARC reports for authentication failures and 'suspected spam' temporary errors from Apple.
Common pitfalls
Failing to whitelist your domain with Apple, leading to hard bounces for Private Relay addresses.
Ignoring DMARC failures or '5.7.1 transformation error' bounces, which indicate deliverability issues.
Misinterpreting inflated open rates due to Apple's Mail Privacy Protection, rather than actual engagement.
Expert tips
If you are experiencing bounces from Apple Private Relay addresses, the first step is always to verify your domain whitelisting in the Apple Developer Account, as this is a common prerequisite.
Understanding that the 'From' name remains visible, even if the email address is masked, can help maintain brand consistency and sender identity.
Even if your ESP states they don't explicitly 'support' Private Relay, as long as you control your sending domain and can whitelist it with Apple, and your ESP offers custom return paths, you should be able to send emails effectively.
Expert view
Expert from Email Geeks says the email address you send from is encoded in the local part of the From: address as the user sees it, which means both the From name and the encoded actual ID are impacted.
May 16, 2024 - Email Geeks
Marketer view
Marketer from Email Geeks says they encountered an issue where their ESP claimed not to support Apple Private Relay.
