MX Records Checker
Look up the mail servers for any domain. See which provider handles its email and whether addresses on it can receive mail at all.
REST API
All of UserCheck's email and domain intelligence in a fast and simple API.
$ curl https://api.usercheck.com/domain/google.com
{
"mx": true,
"mx_records": [{ "hostname": "smtp.google.com", "priority": 10 }],
"mx_providers": [{ "slug": "google", "type": "mailbox", "grade": "professional" }]
}1,000 free credits each month · no credit card required.
What an MX lookup tells you
An MX (mail exchange) record is the DNS entry that says which server handles a domain's email. A lookup takes one DNS query and tells you two things: whether the domain can receive email at all, and which provider runs it.
Domains that can't receive email
A domain with no MX records isn't configured to receive email, so a confirmation message bounces and the address can't be used. At signup that's a reason to reject it and ask for another: the domain is either misconfigured or made up.
Identifying the email provider
When a domain does have MX records, the hostnames usually reveal who runs its email. smtp.google.com means Google Workspace, mail.protection.outlook.com means Microsoft 365; others map to Fastmail, Zoho, or Proton. UserCheck matches these against known services and returns the provider, which is useful context on a signup: a recognized provider is reassuring, while an unfamiliar or self-hosted mail server is worth a closer look. It also tells a regular mailbox from a forwarding relay.
Checking it from your code
Every /domain and /email lookup returns mx (a boolean), mx_records (hostnames with priorities), and mx_providers (the detected services). Validate deliverability or detect the provider in one call. See the API documentation for examples.
Common questions
What is an MX record?
A DNS record that tells the internet which mail server handles email for a domain. A domain can list several, each pointing to a different server.
What does the priority number mean?
It sets the order servers are tried. Lower wins: a server at priority 10 is tried before one at 20. Backups sit at higher numbers, so they're only used when the primary is unreachable.
What if a domain has no MX records?
It can't receive email, so anything sent to [email protected] bounces. That also makes a missing MX a useful fraud signal, since a real business almost always has mail configured.
How does UserCheck identify the email provider?
By matching the MX hostnames to known services: smtp.google.com for Google Workspace, mail.protection.outlook.com for Microsoft 365, plus Fastmail, Zoho, Proton, and many more. The provider comes back next to the raw records.
Should I block signups from domains with no MX records?
Usually, yes. With no MX records, confirmation emails to that address bounce, so even a legitimate user is unreachable. Addresses generated by bots and fake-signup scripts also tend to use domains with no mail configured. If a hard block is too strict for your flow, ask the user for a different address instead.
Can I check MX records from my code?
Yes. Both /domain/{domain} and /email/{email} return mx, mx_records, and mx_providers. The API documentation has examples.