How often do these domain lists change for major providers?

Major email providers constantly update their domain portfolios, merge services, or retire older domains. For instance, Yahoo has integrated AOL into its domain structure. Staying updated requires continuous monitoring of official announcements, industry news, and deliverability blogs that track these changes.

Why is it important to know all subdomains or associated domains?

Knowing these domains helps you segment your email lists more effectively, troubleshoot deliverability issues, and ensure your email authentication (SPF, DKIM, DMARC) is correctly configured for all relevant domains. This is critical for maintaining good domain reputation and inbox placement.

Does iCloud Private Relay use a specific domain I should be aware of?

Yes, Apple's iCloud Private Relay generates unique, randomized email addresses that often use the privaterelay.appleid.com domain. While technically a distinct domain, it operates under Apple's umbrella and is an important consideration for deliverability to Apple's user base .

Where can I find an exhaustive list of all domains for these providers?

While you can find lists online, they are rarely exhaustive or perfectly up-to-date due to the dynamic nature of these domains. The best approach is to combine static lists with ongoing monitoring of your email campaigns to identify any deliverability issues related to specific domains.

How do blocklists affect emails sent to these provider domains?

If your domain (or IP) is listed on a blocklist (or blacklist), it can significantly impact your email deliverability, often causing emails to be rejected or sent to spam folders by these major providers. Monitoring your blocklist status and promptly requesting delisting if necessary is crucial.

What are the lists of subdomains for major email providers like Google, Microsoft, Yahoo, and Apple? - Technical - Email deliverability - Knowledge base

Understanding the email ecosystem involves knowing which domains belong to the major email providers. While we often think of Gmail, Outlook, Yahoo, and Apple as distinct entities, they often manage a wider array of subdomains or legacy domains. For anyone dealing with email deliverability, knowing these associated domains is crucial. It helps in segmenting audiences, troubleshooting issues, and ensuring compliance with sender requirements.

While some of these domains might be obvious, others are remnants of past mergers or acquisitions that continue to be used by millions of users. My goal is to shed light on these less obvious domains, providing a comprehensive view of the major mailbox providers' email footprints. This knowledge is especially important when you are monitoring your blocklist status or dealing with bounces, as understanding the full scope of domains can streamline your efforts.

Understanding major email provider domains

The major players in the email space, often referred to as MAGY (Microsoft, Apple, Google, Yahoo), manage a vast number of domains. These aren't just the primary domains we use daily, but also a collection of legacy domains, country-specific domains, and sometimes even domains acquired from other services. Understanding this full spectrum is vital for email marketers and deliverability professionals.

For instance, Spam Resource provides a helpful overview of these domains, though it's important to remember that such lists are dynamic and can quickly become incomplete. Companies frequently update their domain portfolios, merge services, or retire older domains, making continuous monitoring a necessity.

These domains are not always subdomains in the technical sense, but often distinct top-level domains that function under the same email provider's umbrella. When you send email, the recipient's mailbox provider will assess your sender reputation based on your domain and IP address, among other factors. Being aware of the domains that fall under these major providers helps in segmenting your lists and tailoring your sending strategy.

Domain lists for top providers

Let's dive into the specifics of the major players. Each has a core set of domains and a scattering of others that are still in active use.

Google

Google primarily uses gmail.com for its free consumer email service. However, it's also worth noting that many businesses use googlemail.com, particularly in certain regions like the UK, as an alias that resolves to the same inbox. For those leveraging Google Postmaster Tools, remember that your sender reputation is often aggregated across various factors, not just one domain.

Microsoft

Microsoft maintains a broader range of domains due to its history and acquisitions. The most common are outlook.com, hotmail.com, and live.com. Other domains like msn.com are also part of their ecosystem. When Outlook rolled out its new sender requirements, it affected all domains under their purview, emphasizing the importance of a comprehensive understanding.

Yahoo (including AOL)

Yahoo Mail includes yahoo.com as its primary domain. However, due to its acquisition of AOL, domains like aol.com are also part of its network. Other legacy Yahoo domains include ymail.com and rocketmail.com. Understanding which blacklists Yahoo Mail uses for its filtering is also crucial, as a listing can impact all associated domains.

Provider	Primary Domains	Associated Domains
Google	gmail.com	googlemail.com
Microsoft	outlook.com, hotmail.com	live.com, msn.com
Yahoo (incl. AOL)	yahoo.com, aol.com	ymail.com, rocketmail.com
Apple	icloud.com	me.com, mac.com, privaterelay.appleid.com

This table outlines the primary and key associated domains, but it's important to remember that these lists can be quite extensive, especially when accounting for regional or older domains. My experience has shown that keeping a dynamic list of major free email provider domains is a continuous task.

Apple and other significant players

Apple's email presence has grown significantly, particularly with the introduction of iCloud Mail and its privacy-focused features like iCloud Private Relay. While icloud.com is the most prominent, legacy domains such as me.com and mac.com are still in use and fall under Apple's domain management. For more details on Apple's domains, Spam Resource has a list.

A particular challenge with Apple is the iCloud Private Relay, which can generate unique, randomized email addresses for users. These addresses often use the privaterelay.appleid.com domain. While not subdomains in the traditional sense for your sending, they represent a significant portion of Apple's email traffic and require careful handling to avoid bounces to Apple domains or other deliverability issues. Businesses need to ensure their email authentication protocols, such as SPF, DKIM, and DMARC, are robust enough to handle these diverse sending scenarios.

Furthermore, other ISPs and smaller email providers also operate their own sets of domains and subdomains. While not as dominant as the MAGY group, they still represent a segment of your audience and require similar attention to deliverability. Keeping an eye on the overall email landscape is key to maintaining high inbox placement rates.

Impact on email deliverability and authentication

Knowing the various domains used by major email providers isn't just academic, it has direct implications for your email deliverability. Each provider (and their associated domains) has specific policies and algorithms that determine whether your emails land in the inbox, the spam folder, or get bounced outright. This is where proper email authentication setup for your sending domains becomes paramount.

The importance of subdomains

Using dedicated email subdomains for different sending types (e.g., transactional, marketing, notifications) helps isolate your sending reputation. If one type of email experiences deliverability issues, it won't necessarily impact other types of email sent from different subdomains. This strategy is a cornerstone of robust deliverability, especially when dealing with the varied policies of major mailbox providers.

Ensuring your DNS records are correctly configured for each subdomain is essential for proper authentication.

Proactive monitoring

Monitor blocklists: Regularly check if your sending IPs or domains are listed on any email blacklists (or blocklists).
Analyze bounces: Pay attention to bounce messages, as they often indicate specific issues with particular domains or providers. This can help you identify if your emails are failing to reach their destination.
Use feedback loops: Register for feedback loops with major providers to receive notifications when users mark your emails as spam. This can provide valuable insights into recipient behavior and help you adjust your sending practices.

By actively managing your sender reputation across these diverse domain landscapes, you can significantly improve your deliverability rates and ensure your messages reach their intended recipients.

Moreover, many providers have distinct subdomains for different functions, such as sending notifications (mail.domain.com) or specific marketing campaigns. Understanding the purpose of these various subdomains for email marketing deliverability can help you manage your sending practices more effectively and avoid having your emails flagged as spam.

Navigating the email domain landscape

Understanding the landscape of email domains and subdomains used by major providers is an ongoing task. These lists are not static, but rather dynamic entities that evolve with mergers, acquisitions, and new service offerings. Staying informed is essential for maintaining robust email deliverability.

By having a clear picture of these domains, you can better manage your sender reputation, optimize your email authentication, and ultimately ensure your messages reach their intended recipients without falling victim to spam filters or blocklists. Ongoing vigilance and adaptation are key to success in the complex world of email deliverability.

Views from the trenches

Best practices

Always maintain separate subdomains for transactional and marketing emails to protect sender reputation.

Regularly check your domain's status with Google Postmaster Tools and other provider-specific dashboards.

Implement DMARC with a monitoring policy to gain visibility into your email authentication results.

Keep your recipient lists clean and updated to minimize bounces and spam complaints.

Common pitfalls

Assuming all emails to major providers are treated the same, regardless of their specific domains.

Ignoring legacy domains (e.g., hotmail.com, me.com) and only focusing on primary domains.

Failing to monitor DMARC reports, missing critical authentication issues with your emails.

Not segmenting email sending by type, which can lead to reputational contamination.

Expert tips

Use different IPs and domains for different types of mail, keeping a close eye on their performance.

For Yahoo and Microsoft domains, pay close attention to bounce rates and spam complaint feedback loops.

The email landscape is dynamic; regularly check for updates on provider policies and domain lists.

Don't rely solely on automated tools; manually review your sending data for subtle deliverability trends.

Expert view

Expert from Email Geeks says a comprehensive list of domains can never be truly complete due to their dynamic nature. It is more about understanding the overall ecosystem and monitoring how your emails are performing across different providers.

2023-02-10 - Email Geeks

Marketer view

Marketer from Email Geeks says they use these domain lists to understand the percentage of their database that belongs to each major provider, which helps in audience segmentation.

2023-02-10 - Email Geeks