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 5.88 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.
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.
Methodology and limitations
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 published census of B2B mail providers, measured across millions of business domains with an MX record. The full population, method and limitations are documented in who actually receives B2B email.
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.