How can I determine if a company's email is using Gmail or Yahoo under the hood?
Summary
What email marketers say11Marketer opinions
Email marketer from Zoho explains that you can configure a custom email address and then you need to update your MX records for it to work.
Email marketer from Reddit suggests performing a reverse DNS lookup on the IP address of the mail server. This can reveal the organization that owns the IP, which often corresponds to the email provider.
Marketer from Email Geeks shares a command line script to find the host of an email domain.
Email marketer from Stack Overflow explains that you can use `nslookup -type=mx domain.com` to find the mail exchange server for a domain, which will often indicate if they are using Google Apps (now Workspace) based on the MX record values.
Email marketer from Namecheap explains if you have a domain name then most email providers can be used to send emails under that domain name. These include private email, shared hosting, VPS and dedicated servers or through using a third party like Google Workspace or Microsoft 365.
Email marketer from Reddit says that you can use online tools like `whatsmydns.net` or `centralops.net` to look up MX records and other DNS information, and the MX records would be the most reliable way to see what service they are using.
Email marketer from Reddit explains that examining the email headers can reveal the sending server. Headers like 'Received:' often include the server name, which can hint at whether it's Gmail, Yahoo, or another provider.
Email marketer from Super User responds that the MX records are the definitive method to find the mail server provider. While the user can hide who sends the emails, they can not hide where to send emails. It is possible for companies to relay through their own system and obfuscate the final sending server.
Marketer from Email Geeks shares that you can check the MX record with a tool and mentions Alfred product, Inbox Monster and Validity also offer this feature in their list analyzers.
Email marketer from DigitalOcean shares that the MX records are used to route emails to the correct servers, so checking these will let you see who is hosting the emails.
Email marketer from Whois explains that you can perform an MX Lookup and enter the domain name you would like to find the host for. This will provide the hostname and the IP address.
What the experts say3Expert opinions
Expert from Email Geeks shares that for whitelabel services, you may need to investigate IP addresses, reverse DNS, IP block ownership, server banners, and TLS certificate ownership to identify the actual provider.
Expert from Email Geeks explains that the sending systems are in the SPF record and receiving system is in the MX record.
Expert from Word to the Wise explains that the MX records will show which provider they are using and tools such as MXToolbox, whatsmydns or HostedEmail.com can be used to provide this information.
What the documentation says3Technical articles
Documentation from Google Admin Toolbox shares that the MX records should point to Google servers such as ASPMX.L.GOOGLE.COM if they are using Google Workspace. You can use the MX Lookup tool to check these records.
Documentation from MXToolbox explains that using their MX Lookup tool, you can enter a domain name and it will show you the MX records, which can help determine if the domain uses Google Workspace, Yahoo, or another email provider.
Documentation from KDnuggets outlines the various options for a business email host. These are split into three groups, Self-Hosted, Email Hosting Provider and Hosted Email Services. Hosted Email Services are Gmail (Google Workspace) or Outlook (Microsoft 365).