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🏢 35+ ESPs · Live MX Lookup · Category Detection · Multi-ESP

ESP Finder

Free ESP Finder — identify which email service provider any company uses by querying their MX records. Detects Google Workspace, Microsoft 365, Mailchimp, SendGrid, HubSpot, Klaviyo, and 30+ more providers instantly.

✓ 35+ ESP signatures✓ Live MX lookup✓ Category tagging✓ Multi-ESP detection✓ Raw MX records✓ No signup
Enter domain or email address

Live MX lookup via Cloudflare DoH (Google DoH fallback). Results reflect current DNS — nothing stored or logged.

How it works

Free ESP finder — detect email service provider from domain or email address

Every domain that receives email publishes MX (Mail Exchanger) records in its DNS configuration, pointing to the mail servers responsible for handling inbound messages. Each major email service provider uses predictable, branded hostnames — Google Workspace routes through aspmx.l.google.com, Microsoft 365 through *.mail.protection.outlook.com, and SendGrid through *.sendgrid.net. By querying these records and pattern-matching against a database of 35+ known providers, this tool identifies which ESP a company uses in seconds.

The lookup is entirely passive — MX records are public DNS data that any mail server in the world queries before delivering a message. The domain owner sees nothing. Many companies route different types of email through different platforms: business email through Google Workspace or Microsoft 365, marketing campaigns through Mailchimp or Klaviyo, and transactional messages through SendGrid or Amazon SES. When this happens, all platforms appear in the results.

Security gateways like Proofpoint and Mimecast are also detected — they sit in front of the primary mail platform and appear as lower-priority MX records. This gives a complete picture of the company's email infrastructure.

What this tool does
ESP
Email Service Providers — platforms for sending marketing or transactional email at scale: Mailchimp, SendGrid, Klaviyo, HubSpot, ActiveCampaign, Brevo.
Business
Full-service business email platforms handling incoming and outgoing mail: Google Workspace, Microsoft 365, ProtonMail, Zoho Mail, Fastmail.
Security
Email security gateways filtering inbound traffic before it reaches the primary mail system: Proofpoint, Mimecast, Barracuda, Sophos, Trend Micro.
Hosting
Web hosting providers that bundle email hosting with domains: GoDaddy, Namecheap, IONOS/1&1, Rackspace.
ISP
Internet service providers offering email as part of a broader internet service: Mail.ru, Yandex, regional carriers.
Self-hosted
Mail server hostnames that don't match any known provider — likely custom infrastructure (Postfix, Exim, Exchange on-premise, etc.).
Examples

ESP detection examples -- MX patterns and what they reveal

These are the most common MX record patterns and the ESP each one identifies. Try entering any of these domains in the tool.

Google Workspacegoogle.com -- Gmail / Google Workspace MX pattern
Domain: google.com MX: aspmx.l.google.com (priority 1) alt1.aspmx.l.google.com (priority 5) ESP: Google Workspace Type: Enterprise / Business Email

Google Workspace domains are identified by MX records pointing to aspmx.l.google.com and alt*.aspmx.l.google.com. This is distinct from personal Gmail (which shares the same infrastructure). Google Workspace is the most commonly detected ESP in B2B prospecting and is used by millions of businesses globally.

Microsoft 365microsoft.com -- Exchange Online MX pattern
Domain: microsoft.com MX: microsoft-com.mail.protection.outlook.com ESP: Microsoft 365 (Exchange Online) Type: Enterprise / Business Email

Microsoft 365 domains route inbound email through *.mail.protection.outlook.com. This pattern is instantly recognisable and indicates Exchange Online. Microsoft 365 is the most widely deployed business email platform globally, particularly dominant in enterprise, finance, legal, and government sectors.

Mailchimpsender.com -- Mailchimp transactional MX pattern
Domain: example-sender.com MX: mta.mailchimp.com ESP: Mailchimp (Mandrill) Type: Marketing / Transactional Email Platform

Mailchimp's transactional infrastructure (Mandrill) uses mta.mailchimp.com as the MX record for customer sending domains. Detecting Mailchimp indicates the company actively invests in email marketing -- useful context for sales outreach targeting marketing technology buyers.

Self-Hostedlarge-enterprise.com -- custom mail server infrastructure
Domain: large-enterprise.com MX: mail.large-enterprise.com ESP: Self-Hosted / Unknown Type: Custom Infrastructure

When MX records point to the company's own domain rather than a known ESP's infrastructure, the company runs its own mail server. Large enterprises, universities, government agencies, and organisations with strict data sovereignty requirements commonly self-host. The raw MX hostname is shown so you can investigate further.

Dual Layerenterprise.com -- security gateway in front of Microsoft 365
Domain: enterprise.com MX 1: enterprise.com.ppe-hosted.com (Proofpoint gateway) MX 2: enterprise-com.mail.protection.outlook.com (M365) ESP: Proofpoint + Microsoft 365

Two ESPs in MX results indicate a layered architecture: a security gateway (Proofpoint) receives all inbound email first, filters it, then passes clean messages to the mail platform (Microsoft 365). Common at large enterprises with strict security requirements. The gateway has lower MX priority so it is contacted first.

FAQ

Frequently asked questions about ESP detection and email provider lookup

What is an ESP Finder?
An ESP Finder is a tool that identifies which email service provider a company uses by querying the domain's MX (Mail Exchanger) DNS records and matching the returned mail server hostnames against a database of known provider signatures. It can reveal whether a company uses Google Workspace, Microsoft 365, Mailchimp, SendGrid, HubSpot, or any of 35+ other recognised providers. The ESP is identified by matching MX record hostnames against a database of known provider signatures -- results appear within seconds of the DNS query completing.
How does ESP detection work technically?
Every domain that receives email publishes MX records in its DNS configuration. These records point to the mail servers responsible for handling inbound messages. Each major email service provider uses predictably named hostnames — for example, Google Workspace domains point to aspmx.l.google.com, Microsoft 365 points to *.mail.protection.outlook.com, and SendGrid uses *.sendgrid.net. This tool queries those records via Cloudflare DNS over HTTPS (with Google DoH as fallback) and pattern-matches the results against its ESP database.
Why would I want to know which ESP a company uses?
There are several use cases: competitive research (understanding a competitor's email infrastructure and sophistication), sales intelligence (ESP choice is often a proxy for company size and marketing maturity), email deliverability troubleshooting (knowing the receiving infrastructure helps diagnose delivery issues), integration planning (verifying a contact's platform before proposing an API integration), and security analysis (detecting security gateways in front of a company's primary mail system).
Can a domain use multiple ESPs simultaneously?
Yes — this is relatively common among larger companies. A typical setup might use Microsoft 365 or Google Workspace for internal business email and a security gateway like Proofpoint or Mimecast in front of it, while also routing marketing campaigns through Mailchimp or Klaviyo and transactional messages through SendGrid or Amazon SES. When this happens, multiple ESPs appear in the results, each identified from a distinct MX record.
What does it mean when no ESP is detected?
If MX records exist but no ESP is recognised, the domain likely uses a self-hosted mail server (running on their own infrastructure with a custom hostname), an uncommon or regional provider not yet in the database, or a white-label email platform that doesn't use the provider's own hostnames. The raw MX records are always shown so you can investigate the hostname directly.
What's the difference between an ESP and an email security gateway?
An ESP (Email Service Provider) is the platform that actually sends and stores email — Google Workspace, Microsoft 365, Mailchimp, etc. An email security gateway (Proofpoint, Mimecast, Barracuda) sits in front of the primary mail system and filters inbound traffic for spam, phishing, and malware before passing clean messages to the underlying platform. When a domain uses both, both will appear in the MX records — the gateway typically has lower MX priority (lower number = higher priority) so it receives email first.
How accurate is ESP detection?
Detection accuracy is very high for major providers with well-known MX patterns. The database covers 35+ ESPs representing the majority of business email deployments globally. Accuracy is limited for self-hosted servers, highly customised enterprise setups, or very new providers not yet in the database. The raw MX records are always displayed, allowing manual verification in cases where automatic detection fails.
Does querying a domain's MX records alert the domain owner?
No — MX record lookups are completely passive and invisible to the domain owner. MX records are public DNS data that any email server in the world queries before sending a message to that domain. No connection is made to the mail server itself, and nothing is logged on the target's side. The lookup is performed via Cloudflare's public DNS resolver.
Can I use this to find which ESP a competitor uses for their email campaigns?
Partially — this tool detects the sending infrastructure via MX records, which reveals the receiving platform and often the primary ESP. However, MX records show inbound mail routing, not necessarily the outbound marketing platform. To identify the exact ESP used for outbound campaigns, you'd need to inspect the email headers of a received message from that company (using the Email Header Analyser tool). Headers reveal the originating SMTP server, DKIM selector, and Return-Path domain, which together identify the sending ESP.
What does it mean if a domain has no MX records?
A domain with no MX records cannot receive inbound email. This is common for domains used exclusively for web content, subdomains used for other purposes, recently registered domains that haven't been configured yet, parked domains, or domains used only for sending (which requires SPF/DKIM but not MX records). It does not necessarily mean the company doesn't send email — just that this particular domain isn't set up to receive it.
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