Recon / Public data only
Domain Recon
Find out what a domain runs on: a Microsoft 365 tenant, Google Workspace, an identity provider such as Okta, or another mail host. Enter a domain, an onmicrosoft.com name, or an email address. For a Microsoft tenant the report also gives the tenant ID, the cloud, every domain Exchange lists, how each one signs in, the mail records, and the Microsoft services a domain advertises. Every domain also gets its public registration (WHOIS) record. Everything comes from public endpoints and DNS.
Only the domain leaves your browser, so the part of an email address before the @ is never sent. No sign-in and no user lookups. What this site keeps.
01
Platforms
Microsoft 365, Google Workspace, Okta and other identity providers, and other mail hosts, each with the record that names it.
02
Microsoft tenant
Tenant ID, cloud, and region, plus each domain Exchange Online lists with its initial onmicrosoft.com name.
03
Managed or federated
How each domain signs in, and which identity provider a federated domain redirects to.
04
Mail policy
MX routing, SPF, DMARC, the Exchange Online DKIM selectors, MTA-STS, TLS-RPT, and BIMI.
05
Service footprint
Teams, Intune, Entra device registration, SharePoint, and OneDrive names in DNS, plus verification tokens.
06
Raw evidence
Every request and record behind the report, ready to copy as JSON or a short summary, or to download as a PDF.
Questions
Finding a Microsoft 365 tenant ID, and what else a domain shows
How do I find a Microsoft 365 tenant ID from a domain?
Type the domain into the lookup above. The tenant ID is the GUID inside the issuer of Microsoft's public OpenID Connect discovery document for that domain, at login.microsoftonline.com/<domain>/v2.0/.well-known/openid-configuration, which is the page this tool reads. It needs no sign-in and no access to the tenant. The tenant ID is the same value Microsoft Entra ID, formerly Azure Active Directory, calls the Directory (tenant) ID, so this also finds an Entra or Azure AD tenant ID from a domain.
What is an onmicrosoft.com domain?
A Microsoft 365 tenant in the worldwide cloud, GCC included, starts with an initial domain named name.onmicrosoft.com. Enter that name, or just the name, to look the tenant up. The report shows the initial domain whenever Exchange Online lists it. US Government GCC High and DoD tenants use name.onmicrosoft.us, which this lookup treats as an ordinary domain.
How can I tell whether a domain uses Microsoft 365?
Look at where its mail goes and whether Microsoft knows the domain. An MX record ending in mail.protection.outlook.com, Autodiscover and Teams records that point at Microsoft, and a tenant ID from Microsoft's sign-in discovery all point to Microsoft 365, formerly Office 365. A tenant ID shows the domain belongs to a Microsoft Entra tenant, and organizations that only use Azure have one too. A mail gateway in front can hide the MX record, so the list of domains Exchange Online reports is the stronger check there. The report shows each one.
Can it tell whether a domain uses Google Workspace or Okta?
Google Workspace shows up in DNS: an MX record at google.com, or a DKIM key at google._domainkey, the selector Google uses unless an admin picks another. Okta and other identity providers show up when Microsoft sends a domain's sign-in to them. An identity provider used only for other apps publishes nothing this lookup can read, so the report names only what it finds evidence for.
Is a domain managed or federated?
Microsoft's sign-in discovery reports each domain as managed, where Microsoft Entra checks the sign-in, or federated, where sign-in is sent to another identity provider such as AD FS or Okta. The report names the provider when it recognizes the sign-in address.
Does this look up users or contact the domain's servers?
No. It never asks whether an account exists, and it never connects to the domain's own web or mail servers. For an email address it uses only the part after the @, and the part before it stays in your browser.
What can a public lookup not show?
Anything behind a sign-in: users, licenses, Conditional Access policies, or tenant settings. DNS shows what a domain publishes, not what is enforced, and a tenant can leave records unpublished.
Questions about what a report means for your own tenant? Use the contact form. To find out why one message was delayed or sent to Junk, paste its header into the email Header Analyzer.
Method
Where the data comes from
Every request goes to one of the hosts below. The name you enter becomes a DNS query or a path on those hosts and never a server this site connects to. The registry server is picked from a copy of IANA's list kept in the site's code.
Microsoft sign-in discovery
login.microsoftonline.com
The tenant ID, region, cloud, organization name, and how each domain signs in.
Exchange Autodiscover
autodiscover-s.outlook.com
The domains Exchange Online lists for the tenant, including its onmicrosoft.com name.
Public DNS over HTTPS
cloudflare-dns.com, then dns.google if it fails
MX, SPF, DMARC, the Exchange Online and Google DKIM selectors, MTA-STS, TLS-RPT, BIMI, service records, name servers, verification tokens, and the SharePoint and OneDrive host names.
US Government authority
login.microsoftonline.us
Asked only when Microsoft's sign-in discovery says the tenant uses it.
Registry RDAP, the successor to WHOIS
the registry's server from IANA's bootstrap list, such as rdap.verisign.com for .com
The registrar, registration and expiry dates, status, name servers at the registry, and any contact details the registry publishes.
Not contacted: the domain's own web or mail servers, its registrar's RDAP server, any user account, and the SharePoint or OneDrive sites themselves. Those names are checked in DNS only. A lookup makes about 40 requests at most, and each visitor gets six lookups a minute.