What tools and methods can be used to identify the mailbox provider associated with an email address or domain?
Summary
What email marketers say12Marketer opinions
Email marketer from Email Deliverability Blog suggests checking the IP addresses found in the email header against blocklists and reputation databases. While not directly identifying the provider, it can give clues based on the IP range and associated organizations.
Email marketer from StackExchange shares that you can examine the email header to see where the email originated from. Often, this will indicate the mailbox provider through the 'Received:' headers and the originating server's hostname.
Email marketer from TrustPilot describes using ZeroBounce to verify email addresses. ZeroBounce identifies the email provider along with other data points related to the address's validity and deliverability.
Marketer from Email Geeks mentions their product can identify where an email address is hosted (Gmail/Outlook) and offers a walkthrough.
Email marketer from Reddit recommends using online MX lookup tools like whatsmydns.net or MXToolbox. Enter the domain name, and the tool will show the MX records, which indicate the email service provider.
Marketer from Email Geeks shares that grouping emails accurately by mailbox provider involves grouping by MX records, but this method can change, especially for business domains.
Marketer from Email Geeks suggests doing MX lookups to identify mailbox providers and recommends tools like securry.com for bulk lookups. They explain how different providers (Office365, GSuite, webmail hosts) have different MX records.
Email marketer from SuperUser warns that sometimes a domain might have a hybrid email setup, where some mailboxes are on one provider (e.g., Exchange) and others are elsewhere. MX records will only show where the primary mail is handled, not necessarily all mailboxes.
Email marketer from Quora shares that MXToolbox can be used to look up MX records, which often reveal the mailbox provider. For example, if the MX record points to google.com, it's likely a Gmail or GSuite address.
Email marketer from Webmaster Forum says you can use WHOIS to look up the domain and see who it is registered with. Although it doesn't directly indicate the email provider, it may give clues, especially if the registrar also provides email services.
Email marketer from Neil Patel Blog shares that you can use email lookup tools, some of which provide information about the email provider associated with an email address. These tools often rely on MX record lookups and other data sources.
Email marketer from Email Marketing Forum suggests using email validation services like Email Hippo, which can identify the mailbox provider as part of its email verification process.
What the experts say6Expert opinions
Expert from Email Geeks explains their code optionally takes email addresses, strips the local parts out in JavaScript in the browser, uploads the domains for MX stitching, then reassembles the data back into the original CSV for download, all in the browser.
Expert from Word to the Wise, Laura Atkins, explains that SPF (Sender Policy Framework) records, while primarily for authentication, also offer clues to the provider. Analyzing the 'include:' mechanisms in an SPF record can reveal the third-party senders or providers a domain uses.
Expert from Email Geeks suggests that manually maintaining the classification code is the best approach, emphasizing the need to handle messy data.
Expert from Email Geeks has a version of their internal code intended to be made publicly available if it's useful, intended as a CSV upload to a web page for results. Maintaining data privacy in the process is seen as slightly tricky.
Expert from Word to the Wise Editorial Team responds that many diagnostic tools can be used, for example looking at the headers in emails can reveal vital information to see where an email has originated from.
Expert from Email Geeks mentions they have internal code that performs DNS lookups, normalizes them, and classifies MX records by provider, but it's not currently public.
What the documentation says5Technical articles
Documentation from Microsoft Learn details how to check DNS records, specifically MX records, to determine if a domain is using Exchange Online for email services. The MX record will point to outlook.com.
Documentation from RFC Editor explains that RFC 5321 outlines the Simple Mail Transfer Protocol (SMTP) which governs how email is transmitted. Understanding SMTP and reviewing email headers based on these standards can help trace the path of an email and identify the involved mail servers.
Documentation from EmailStandards.org describes the structure and fields within email headers, including 'Received' fields that trace the email's journey through different servers. Examining these headers can help identify the originating mail server and associated provider.
Documentation from IONOS explains that MX (Mail Exchange) records specify the mail servers responsible for accepting email messages on behalf of a domain. Looking up these records can identify the email service provider.
Documentation from Google Workspace Admin Help explains how to use the Google Admin Toolbox Dig feature to look up MX records for a domain. This will indicate if the domain uses Google Workspace for email.