How can I determine if a company's email is using Gmail or Yahoo under the hood?

Key findings

• MX records: The most direct way to identify the underlying email provider is by checking the domain's Mail Exchange (MX) records. These DNS records specify the mail servers responsible for accepting incoming emails for a domain. If the MX records point to Google's (e.g., gmail.com, google.com) or Yahoo's (e.g., yahoo.com, verizonmedia.com) servers, the company uses their infrastructure for receiving email.
• SPF records: Sender Policy Framework (SPF) records also provide clues about outgoing mail servers. While MX records show who receives mail, SPF records indicate which mail servers are authorized to send mail on behalf of the domain. If Google or Yahoo are listed in the SPF record, they are likely involved in sending.
• Whitelabeling: Some larger mailbox providers (MBPs) or email service providers (ESPs) offer whitelabel services, making it less obvious from a simple MX lookup that another company hosts the email. This requires deeper investigation into IP addresses and TLS certificates, which we discuss in our article about identifying mailbox providers.
• Email headers: Examining email headers (particularly the Received: and Authentication-Results: fields) can reveal the journey of an email and the servers involved. This is detailed in our guide on identifying sending platforms.
• Authentication standards: Both Gmail and Yahoo have reinforced their requirements for strong email authentication using SPF, DKIM, and DMARC. Understanding these configurations can also indirectly indicate the underlying provider's practices. More information on this can be found on the official Google blog.

Key considerations

• Domain vs. provider: A company using a custom domain (e.g., yourcompany.com) does not mean they host their own email. Many businesses leverage Gmail (Google Workspace) or Yahoo (via various hosting solutions) for their email infrastructure due to reliability and feature sets.
• Tool limitations: While various online tools can check MX and SPF records quickly, some providers implement configurations that obscure their identity. In such cases, more advanced analysis is required.
• Dynamic changes: Companies can change their email providers, so an older lookup might not reflect current configurations. Regular checks are important for up-to-date information.
• Deliverability impact: Knowing the underlying email provider helps anticipate deliverability challenges and understand specific requirements from Google and Yahoo, especially concerning bulk sending and authentication, as highlighted by Mailgun's blog on inbox requirements.

Key opinions

• Use of MX records: Many marketers begin their investigation by checking the MX records of a domain to see if they point to Google, Yahoo, or other common providers. This is often the quickest and most straightforward method.
• Leveraging online tools: Online DNS lookup tools are popular for their ease of use in quickly retrieving MX and SPF information without needing command-line knowledge. These tools can automate much of the lookup process.
• SPF for sending: While MX records indicate receiving services, SPF records are seen as key for understanding which services are authorized to send email. Marketers will examine SPF records for entries related to Google or Yahoo.
• Consideration of whitelabeling: Some marketers acknowledge that whitelabel services make direct identification challenging, requiring more advanced technical steps beyond basic DNS lookups. This aligns with approaches for identifying mailbox providers.
• Technology overview tools: Some marketers also use broader technology detection tools that scan websites for various technologies, including email providers, offering a simpler overview rather than detailed DNS analysis. This can be a quick way to discover the sending domain and ESP details.

Key considerations

• Accuracy limitations: While useful, relying solely on publicly available DNS records might not always provide a complete or current picture, especially if a company uses a complex email setup or recently migrated services.
• Manual checks versus automation: For individual lookups, manual checks are feasible. For large lists, automated tools become essential due to the impracticality of manual investigation.
• Reputation and compliance: Understanding if Gmail or Yahoo is the underlying provider helps in anticipating specific deliverability rules and maintaining a good sender reputation, crucial for avoiding blacklists and blocklists.
• Deliverability rules: Awareness of Gmail and Yahoo's new sender requirements (like those discussed on the FluentCRM blog) is paramount. Knowing the provider helps marketers comply and improve inbox placement.

Key opinions

• MX records are foundational: The MX (Mail Exchange) record is the go-to DNS record to identify where a domain receives its email. If these records point to Google's or Yahoo's servers, it's a strong sign they are the underlying provider. We cover more on identifying SMTP providers.
• SPF records reveal sending infrastructure: SPF records indicate which IP addresses and domains are authorized to send email on behalf of a domain. This helps identify the sending platform, which might also be Google or Yahoo, or a third-party ESP integrated with them. A basic understanding can be found in our guide to SPF, DKIM, and DMARC.
• Whitelabeling challenges: Experts note that some mailbox providers offer whitelabel services where the underlying host is not immediately apparent from MX records. This requires deeper investigation, such as checking reverse DNS or IP block ownership.
• Advanced technical checks: For hard-to-identify cases, experts suggest connecting to mail servers directly to check banners and TLS certificate ownership, as these can provide definitive clues about the hosting provider.
• DNS records as primary data: Despite challenges, DNS records remain the primary source of information, even if SPF records are not always perfectly maintained. Experts emphasize working with the available data to make informed conclusions.

Key considerations

• SPF record accuracy: The reliability of SPF records in identifying email providers depends on how well companies maintain them. Some organizations might have outdated or incomplete SPF records, complicating the detection process.
• Complexity of self-hosting: Self-hosting email (e.g., on Exchange servers) can introduce significant complexity and potential trauma for IT teams. This often drives companies towards managed services from large providers like Google or Microsoft Outlook.
• Terminal commands for deep dives: For those comfortable with command-line interfaces, specific commands can parse email lists and extract host information to identify underlying providers, even if they're using tools for identifying the mailbox provider.
• No definitive answer for all cases: Even with advanced techniques, there are instances where the underlying email provider remains unclear. Experts concede that sometimes, throwing up one's hands is the only option.

Key findings

• MX record lookup: Documentation from various sources, like Quora, confirms that checking MX records via tools like MXToolbox.com is the standard procedure. If the records show Google or Yahoo hostnames, it implies their service is used.
• Authentication standards: Both Gmail and Yahoo require strong email authentication (SPF, DKIM, and DMARC) for bulk senders. This means even if a company uses a custom domain, their authentication records will reflect the underlying provider if it's Google or Yahoo. Our article on why emails fail delves into this further.
• Sender requirements: Official announcements from Google explicitly state new requirements for bulk senders, including email authentication and spam threshold maintenance. These requirements apply to any domain using their infrastructure, regardless of its custom appearance. More information on this can be found on Google's official blog.
• Domain vs. provider: Documentation often clarifies that an organization's email typically won't directly have domains like @gmail.com or @ymail.com in the email address itself if they are using a custom domain. The underlying service is revealed through DNS.
• Technical methods: Technical forums like Information Security Stack Exchange suggest methods such as connecting to Google mail exchangers on port 25 (SMTP) to test if they accept email for a specific domain, providing a programmatic way to verify the backend.

Key considerations

• Updated requirements: Documentation from Mailgun and Mailjet highlights that new Gmail and Yahoo inbox requirements from 2024 mandate strong authentication. This implies that domains using these providers will have their SPF, DKIM, and DMARC records configured accordingly, offering another method of identification. This is crucial for boosting deliverability rates.
• Consistency of authentication: Yahoo's stance on authentication is consistent with Gmail's, emphasizing that senders must establish strong authentication with either SPF, DKIM, and DMARC for their domains. This provides consistent signals for identification.
• Spam thresholds: Both providers require bulk senders to stay below a reported spam threshold. While not a direct identification method, consistent adherence to these rules by a domain often suggests they are leveraging a compliant service like Google Workspace or Yahoo Business Mail.