Free Email Provider Checker
Find out if a domain is a public provider like Gmail or Yahoo, where anyone can open an inbox. Useful for enforcing corporate-only signups.
REST API
All of UserCheck's email and domain intelligence in a fast and simple API.
$ curl https://api.usercheck.com/email/[email protected]
{
"public_domain": true
}1,000 free credits each month · no credit card required.
What a public provider address tells you
A public email provider is any service where anyone can open an inbox: Gmail, Yahoo, Outlook, iCloud, Proton, GMX, and hundreds of regional ones. Most are free, which is the common name for them, though a few are paid; what they share is that anyone can sign up. The inboxes are real and permanent, which is what separates them from disposable addresses. What a public-provider address doesn't carry is a company: a personal Gmail signup isn't fraud, but there's no organization behind it to identify.
That distinction comes up in a few common flows. B2B tools enforce work-email-only signups so every account maps to a company. Fraud teams send public-provider signups through extra verification. Sales teams score a Gmail lead differently from one on a corporate domain. None of that means blocking Gmail outright; it means knowing which kind of address you're looking at.
Coverage beyond the major providers
Recognizing gmail.com is easy. Misses come from the regional and niche providers that English-language lists tend to skip: web.de and GMX in Germany, mail.ru and yandex.ru in Russia, qq.com and 163.com in China, naver.com in Korea. UserCheck tracks these alongside privacy providers like Proton and Tutanota, and keeps the list current from the domains customers send through the API.
Checking it from your code
Every lookup returns public_domain: true or false, on both the /domain and /email endpoints. Enforce work-email signups, or branch your onboarding, in one call. See the API documentation for examples.
Common questions
What counts as a "free" email provider?
Any service where anyone can open a mailbox: Gmail, Yahoo, Outlook, iCloud, Proton, GMX, and hundreds of regional ones. These are public providers; most are free, which is the everyday name for them, but a few are paid, so the defining trait is open signup rather than price. They're real, lasting inboxes people use as their main address. They just aren't attached to a company.
Is a public provider the same as a disposable one?
No, and it's worth keeping straight. A public provider like Gmail gives someone a permanent inbox they actually live in. A disposable provider like Mailinator hands out a throwaway that's gone in minutes. UserCheck reports them as separate fields: public_domain for public providers, disposable for throwaway ones.
Should I block public email providers at signup?
Usually not outright. For a B2B product, sending public-provider signups down a different path (extra verification, manual review) makes sense. Blocking them entirely turns away solo founders and freelancers who haven't set up a domain yet. Flag rather than ban, unless you have a hard work-email requirement.
Why do people sign up for B2B tools with a Gmail?
Mostly legitimate reasons: a solo founder without a company domain, a freelancer, or someone trying the product before looping in IT. A smaller share are masking who they are. That's why a public-provider hit is a signal to weigh, not a reason to reject on its own.
How complete is the list?
It covers the global providers everyone knows plus the regional ones English-only lists miss, like web.de, mail.ru, qq.com, and naver.com. New providers get added from the domains customers run through the API.
Can I check public-provider status from the API?
Yes. Both /domain/{domain} and /email/{email} include public_domain: true|false, so you can branch your signup logic on it in one call. The API documentation has examples.