Free ESP Checker — Detect Any Domain's Email Provider
Instantly identify which email service provider (ESP) a domain uses. Enter any email address and see the MX-based provider in seconds.
Why Knowing the ESP Matters
What This Tool Detects
Our ESP checker resolves MX records in real time and maps them against known provider signatures.
How to Use the Results
Each detected provider requires a different deliverability approach — here is what to do.
Google Workspace
Use plain-text-friendly HTML and ensure strict DMARC alignment. Google weights engagement heavily — list hygiene is critical before every send.
Microsoft 365
Verify SPF alignment. Microsoft 365 filters aggressively on sender reputation and bulk patterns. Warm up new domains slowly and monitor bounce rates.
Amazon SES or SendGrid
Typical transactional infrastructure. Look for engagement signals and monitor open rates to maintain sender score with these platforms.
Unknown Provider
Proceed with caution. Warm up new senders carefully, monitor for hard bounces, and verify addresses with EmailVerify.io before high-volume sends.
Null MX — No Mail Accepted
Remove immediately. The domain owner has explicitly declared that this domain does not accept email. Any send will generate a hard bounce.
Who Uses This Tool
ESP detection helps anyone who sends email at scale or needs to audit domains.
Sales teams researching prospect companies before outreach
Deliverability consultants auditing client domains
Email marketers segmenting lists by inbox provider
Developers configuring routing rules per recipient provider
Security researchers investigating phishing or spoofed domains
Frequently Asked Questions
What is an email service provider (ESP) checker?
An ESP checker resolves a domain's MX records and maps them against known provider signatures to identify which email platform — such as Google Workspace, Microsoft 365, or Amazon SES — is handling mail for that domain.
How does the ESP checker work?
Enter any email address. The tool extracts the domain portion, queries its MX records via DNS, then matches the MX hostnames against a database of provider patterns to return the detected ESP.
Which email providers can this tool detect?
The tool detects Google Workspace, Microsoft 365, Amazon SES, SendGrid, Mailgun, Zoho Mail, Fastmail, ProtonMail, Mimecast, Proofpoint, iCloud Mail, Postmark, Mailchimp Transactional (Mandrill), Yahoo Mail, GoDaddy Email, Rackspace Email, Cloudflare Email Routing, Yandex Mail, and Tutanota — plus flagging null MX (domain rejects all mail) and unknown providers.
What does 'Unknown Provider' mean?
Unknown means the domain has valid MX records but the mail server hostnames do not match any recognized provider pattern. This is common for self-hosted mail servers (Postfix, Exchange on-premises) or smaller regional providers not in the detection database.
What does 'Null MX' mean?
Null MX (RFC 7505) means the domain owner has explicitly configured a single MX record of '0 .' to declare that the domain does not accept email. Any emails sent to this domain will bounce. Remove these addresses from your list immediately.
Why does knowing the recipient's ESP improve deliverability?
Different ESPs apply different filtering rules. Google Workspace enforces strict DMARC alignment and uses engagement signals heavily. Microsoft 365 filters aggressively on reputation and bulk patterns. Knowing the recipient's ESP lets you tailor your sending strategy — warming up IP addresses differently, adjusting content structure, and timing campaigns around provider-specific behaviors.
Can I use this to detect the ESP of a B2B prospect before cold outreach?
Yes. Sales teams commonly use ESP detection to segment prospect lists by provider before outreach sequences. Google Workspace and Microsoft 365 inboxes respond differently to cold email — knowing which one you are targeting helps you optimize subject lines, sending cadence, and unsubscribe handling.
Does this tool store the emails I enter?
No. The email address is used only to extract the domain for DNS lookup. Nothing is stored, logged for marketing purposes, or shared with third parties.
What if a domain has multiple MX records pointing to different providers?
The tool queries all MX records sorted by priority. Detection runs across all returned hostnames — the first match against a known provider wins. Domains using multiple providers simultaneously (e.g., a backup MX via a different service) are common; the primary (lowest-priority number) provider is returned.
How is this different from email verification?