Paste one domain or up to 50 and see which email provider each company uses, read live from its MX records: Google Workspace, Microsoft 365, Zoho, Proton, Fastmail, or a security gateway such as Mimecast or Proofpoint in front of it. Free, no sign-up, CSV export.
| Domain | Email provider | MX hosts | Note |
|---|
Every domain that receives email publishes MX (mail exchanger) records saying which servers accept its mail. The big providers use recognisable hostnames, so the MX record names the provider:
| Google Workspace | aspmx.l.google.com, smtp.google.com, mx1.smtp.goog, *.googlemail.com |
|---|---|
| Microsoft 365 | <name>.mail.protection.outlook.com, *.mx.microsoft |
| Other mailbox providers | Zoho Mail, Proton Mail, Fastmail, Amazon SES / WorkMail |
| Security gateways | Mimecast, Proofpoint, Cisco Secure Email (IronPort), Broadcom/Symantec (MessageLabs), Barracuda, Cloudflare Email Security, Trend Micro, Sophos, Hornetsecurity, Forcepoint |
| Personal email | Gmail, Outlook.com/Hotmail, Yahoo, iCloud, AOL, GMX, Proton and other free mailbox domains are labelled as personal email, not as a company’s provider |
The provider is taken from the lowest-numbered (highest-priority) MX records, which is where mail is actually delivered; higher-numbered records are only backups. When a security gateway sits in front, the page also reads the domain’s SPF record: if SPF authorises Google Workspace or Microsoft 365, that is noted as the likely mailbox provider behind the gateway. A host we don’t recognise is shown as Other / self-hosted, with the raw MX hosts so you can judge for yourself.
The matching is the same code our Email Security Signals Actor uses for its emailProvider field, so a domain gets the same answer here as in a bulk run.
Privacy: lookups go straight from your browser to Cloudflare’s public DNS-over-HTTPS resolver (cloudflare-dns.com). Nothing passes through our servers, and we don’t store the domains you check.
Look up the MX records of its domain. MX records tell other mail servers where to deliver email, and each big provider uses recognisable hostnames: Google Workspace points at aspmx.l.google.com, Microsoft 365 at <name>.mail.protection.outlook.com. This checker does that lookup for up to 50 domains at once and names the provider.
It segments accounts by ecosystem. If you sell a Google Workspace add-on, a Microsoft 365 integration, a migration service or email security, the MX record tells you whether a company can use your product before you reach out. It also helps with deliverability: Google and Microsoft filter differently, so knowing how a list splits between them helps you plan warm-up and read inbox placement tests.
The company routes inbound mail through a secure email gateway that scans it before passing it on to the real mailbox provider, which the MX record then hides. When that happens this checker reads the domain’s SPF record and, if it authorises Google Workspace or Microsoft 365, notes that as the likely provider behind the gateway. A gateway is also a strong signal of a security-conscious buyer, and it means your cold email passes one more filter.
The domain is not set up to receive email. Strictly, a sending server falls back to the domain’s A record when there is no MX, but almost no real mailbox works that way, so addresses at that domain will usually bounce. A null MX (a single MX record pointing at .) is an explicit statement that the domain accepts no mail at all.
The MX records themselves are exact: they come live from public DNS. The provider name is a match against known hostnames, so a company that runs its own mail servers or uses a smaller host shows as Other / self-hosted with the raw MX hosts listed. The lookup tells you where a domain receives mail; a company can still send some mail through other services, such as a marketing platform.
This page takes up to 50 domains per run. For larger lists, the Email Security Signals Actor on Apify returns the email provider and MX hosts for every domain along with a full DMARC, SPF and DKIM grade, at $0.02 per graded domain, with domains that don’t exist and failed lookups free.
The Email Security Signals Actor runs the same lookup in bulk on Apify and returns the email provider and MX hosts for every domain, together with a full A–F grade on DMARC, SPF, DKIM, MTA-STS, BIMI and DNSSEC and bulk-sender compliance, ready to export as CSV. $0.02 per graded domain; invalid inputs, duplicates, domains that don’t exist and DNS lookup failures are free.
Check a list on Apify →Other free tools: the DMARC, SPF & DKIM checker grades one domain’s email security in your browser, and the ATS checker shows which applicant-tracking system a company hires through.
