Who receives their email?
Enter any company domain. We read its public MX records and identify the mail environment behind it — Google Workspace, Microsoft 365, or a security gateway such as Proofpoint or Mimecast — and what that environment means for legitimate B2B outreach. Queries run in your browser, nothing is stored, no signup.
MX queries run from YOUR browser via Cloudflare and Google DNS-over-HTTPS. ReplyLead receives and stores nothing.
We segment every campaign by receiving environment.
Gateway-protected enterprises and Gmail-hosted SMBs do not behave the same, so we never treat them the same. That is part of how our campaigns are run.
See the mechanics Apply to work with usWhat each environment means for outbound
Google Workspace
The company's mail is hosted by Google. In our published census of B2B business domains, Google Workspace receives mail for 25.84 percent of domains with an MX record. Gmail's filtering weighs sender reputation and engagement heavily, and its bulk-sender rules require authenticated mail. For legitimate outreach: authentication and list quality matter more than clever content tricks.
Microsoft 365
Mail is accepted by Microsoft's Exchange Online protection layer. Microsoft 365 is the single largest B2B environment in our census at 28.48 percent of domains with an MX record. Microsoft weighs domain and IP reputation with its own SmartScreen heritage, and junk-folder placement differs visibly from Gmail. For outreach: warm gradually and watch bounce codes closely, Microsoft tells you more than Google does.
Security gateway
A dedicated filtering appliance - Proofpoint, Mimecast, Barracuda, Cisco and peers - accepts the mail before the company's real tenant ever sees it. Gateways front 6.76 percent of B2B domains in our census, concentrated in enterprise, finance and regulated industries. They filter on policy as well as reputation, so an identical message can be accepted for one company and quarantined for its competitor. For outreach: expect stricter filtering and set expectations per segment, not per campaign. Gateway-fronted domains also answer verifiers differently from direct tenants: in our data they return a catch-all verdict far more often, measured per product in the catch-all rate by receiving mail stack.
Business mail host
Everything else with a real MX record: Zoho, Proton, Rackspace, registrar and cPanel-style hosting, and regional providers. Filtering quality varies widely - some are stricter than Gmail, some barely filter. In aggregate these long-tail hosts receive mail for the remaining roughly 40 percent of B2B domains in our census.
No MX record
The domain does not advertise a mail server. Some domains without MX still receive mail on an A-record fallback, but for outbound purposes a missing MX usually means the address is dead or the company mails from a different domain. Sending to it mostly produces bounces, which damage your sender reputation.
Checking your own domain
Many people land here asking who hosts my email, for a domain they own rather than a prospect's. The lookup answers that from the same public records: enter your own domain and the result names the environment your mail actually arrives through right now, which is the ground truth no old invoice or setup email can contradict.
Three things worth doing with the answer. First, match it against what you pay for: if the result says Google Workspace but you are paying a different email hosting provider, either a migration never completed or someone has changed the records since. Second, if the result is a security gateway, your real host is still behind it; the gateway is a filter your IT team or provider put in front, and mail continues on to whichever host they configured. Third, if there is no MX record at all, your domain cannot receive mail anywhere, and every address on it fails silently.
What this cannot tell you as an owner: how many mailboxes exist, where the data is stored, or who administers the account. Those live inside the provider's admin console, not in public DNS.
Methodology and limitations
What the prevalence figures do and do not tell you. The census shares on this page measure how common a receiving stack is across 9,847,723 domains. That is infrastructure prevalence and nothing more. It does not predict whether any particular message will be accepted, filtered or rejected - that depends on the sender's reputation, authentication, volume and content, and on policy configured per organisation. A gateway share of 6.76 percent means a gateway is present on that share of domains; it says nothing about your delivery odds.
How the classification works
The tool reads the domain's public MX records over DNS-over-HTTPS and matches the exchange hosts against the same provider taxonomy used in our census of B2B mail providers. One rule matters: the gateway wins. A domain behind Mimecast may still be a Microsoft 365 tenant underneath, but we report Mimecast, because the gateway is the machine that accepts or rejects the connection.
What this lookup cannot tell you
MX records are a snapshot of public DNS, not a deliverability guarantee. A custom or white-labeled MX host may not match any known pattern, in which case the tool reports the raw records rather than guessing. It cannot see internal routing behind the first hop, per-company filtering policy, or whether a specific mailbox exists. Ambiguity is reported as ambiguity.
Does this tool store the domains I check?
No. The lookup runs in your browser and the DNS queries go directly from your browser to Cloudflare and Google public DNS over HTTPS. Nothing is sent to or stored by ReplyLead.
Where do the percentages come from?
From ReplyLead's census of B2B mail providers, computed on the 19 July 2026 snapshot of 8,384,502 domains with an MX record. Every count and share in this tool is fixed to that one snapshot so the per-provider figures stay consistent with each other; they are therefore not the current population. The current census, headline provider mix, full method and limitations are documented in who actually receives B2B email. Reply and bounce rates we measured for each environment are in cold email reply rates by email provider. Whether each of the 9,847,723 domains resolved in that snapshot can receive mail at all is published in the email infrastructure index 2026 Q3.
Why does the receiving environment matter at all?
Because deliverability is negotiated with the receiver, not declared by the sender. The same authenticated message meets three different judges at a Gmail tenant, a Microsoft tenant and a Proofpoint gateway. Campaigns that average across them misread their own results - which is why we segment by environment before sending.
Have a delivered message to investigate? Use the email header analyzer to read its reported authentication results and delivery-hop timestamps alongside this domain's MX lookup.