Look up any domain's mail servers and see who runs them.
We list the MX records in priority order and name the provider or security gateway behind them.
Works with a domain or a full email address. We read DNS fresh on every run.
3 of 5 checks pass. Fix SPF first: until SPF passes, this domain falls short of the rules Gmail, Yahoo and Outlook set for bulk senders.
1 MX record. The lowest number is tried first: smtp.google.com at priority 1.
1 smtp.google.com
| Priority | Host | Address |
|---|---|---|
| 1 | smtp.google.com | 142.250.153.26 |
We can set up your next sending domains with all five checks already passing.
We register the domains, create Google Workspace mailboxes with SPF, DKIM and DMARC in place, and connect them to Emailchaser with warm-up switched on. $6 a mailbox a month, plus $3 setup per mailbox and the domain ($16.59 a year for a .com). Ready in 24 to 48 hours.
The check runs on our server against live DNS and 16 public blocklists (3 for domains, 13 for mail server IPs). A list that does not answer is never counted as clean. Nothing you type is stored.
MX records tell the internet where to deliver mail for a domain.
MX records are the DNS entries that route email to the right servers. Looking them up tells you whether a domain can receive mail at all, and which provider runs it. For your own sending domain, that is the question of whether replies to your campaigns can come back. For a domain you are about to email, it is the first sign of whether the address can exist.
The lookup above runs on our server against live DNS, lists the mail servers in priority order, resolves each one to its address, and names the mailbox provider or security gateway behind them. It also runs the SPF, DKIM, DMARC and blocklist checks on the same domain, because an MX record alone says nothing about whether your mail arrives.
The lowest priority number is the server that gets the mail.
Every MX record carries a priority number, and lower means higher priority. A sending server always tries the record with the smallest number first, and only falls back to a higher number if that server cannot be reached. So a domain publishing 10 mail1.example.com and 20 mail2.example.com routes everything to mail1 unless it goes down.
When two records share the same priority, mail is balanced roughly evenly between them. Older Google Workspace domains list five hosts: 1 aspmx.l.google.com, then two at priority 5 and two at 10. Google now gives new domains a single smtp.google.com. Both are correct. The report above sorts the records lowest first, so the top row is the server that actually receives the domain's mail.
The MX hostname usually gives the provider away.
| MX host ends in | Who runs it | What kind |
|---|---|---|
| google.com | Google Workspace | Mailbox provider |
| mail.protection.outlook.com | Microsoft 365 | Mailbox provider |
| zoho.com, zoho.eu | Zoho Mail | Mailbox provider |
| messagingengine.com | Fastmail | Mailbox provider |
| pphosted.com, ppe-hosted.com | Proofpoint | Security gateway |
| mimecast.com | Mimecast | Security gateway |
| iphmx.com | Cisco Secure Email | Security gateway |
| ess.barracudanetworks.com | Barracuda | Security gateway |
| mx.cloudflare.net | Cloudflare Email Routing | Forwarding service |
A security gateway reads every message first and then hands it to the mailbox provider behind it, so the MX tells you the filter, not necessarily where the inbox lives. That matters for cold email: a gateway is one more system that reads your SPF, DKIM and DMARC before a person ever sees the message.
Most of the companies you email put a gateway or a big provider in front of their inbox.
Inbox Rules Index
Who handles inbound mail for the 499 business domains we measure: Proofpoint 33.9%, Microsoft 365 26.1%, Google Workspace 18.8%, Their own servers, or unknown 9.6%, Mimecast 4%. A domain with a security gateway in front of Microsoft 365 or Google Workspace counts as the gateway, because that is the software that reads the message first.
Measured Saturday, 5 September 2026 across 499 real business domains, 10 measurements since 2026-08-10.
On each measurement we look up the published email settings of the same 499 real companies, the kind you send cold email to. This is what they have set up, not a score on your own sending. It does not predict where your mail lands: that is judged against your own domain's records.
An MX record proves the domain can receive mail, not that an address exists.
A domain having MX records means it can receive email, but not that a specific address is real. Catch-all domains accept everything and tell you nothing. When you need certainty about one address, it has to be checked mailbox by mailbox: the free email checker does that for single addresses, and the bulk email verifier for a list. From your own code, 1Lookup, built by the same team as Emailchaser, offers the same check as a bulk email validation API.
The MX record also tells you nothing about who is on the other end of an address. If that is the question you actually have, you can look up the owner of an address from the address itself.
A domain with no MX record usually cannot receive mail at all.
The most common reason is that the domain simply is not set up for email: a parked domain, a redirect-only domain, or one bought purely for a website. Under the mail-routing rules a server may fall back to the domain's A record when there is no MX, so a handful of domains still accept mail without one, but you should not count on it.
Before assuming a domain is dead, rule out the simple causes. Check the spelling, and make sure the domain was not registered or moved in the last hour. And a single record pointing to a bare dot is a null MX (RFC 7505): a deliberate signal that the domain never accepts mail. Our check fails both cases, because a sending domain that cannot receive replies loses every answer to its campaign.
Your own sending domain needs MX, SPF, DKIM and DMARC before it sends.
If you are troubleshooting your own sending, MX is only the first line of the report above. Gmail, Yahoo and Outlook require SPF, DKIM and DMARC from bulk senders (Google, read 6 October 2026), so read the other four rows, or open the SPF, DKIM and DMARC checkers for the full detail.
Sending history is the part no DNS check can show you. A mailbox that has never sent anything has no reputation to spend, which is why warming up the sending mailbox belongs on the same checklist.
Provider hostnames as matched by our provider classifier, the same one the Inbox Rules Index uses.
Common questions about MX records
What is an MX record?
An MX (Mail Exchange) record is a DNS record that tells the internet which servers handle email for a domain, and in what priority order. If a domain has no MX records, it generally can't receive email.
How do I check a domain's MX records?
Type the domain above and press Check domain. The lookup runs on our server against live DNS, lists the mail servers with their priorities, lowest number first, and names the provider or security gateway the hosts belong to (Google Workspace, Microsoft 365, Proofpoint, Mimecast and so on).
Why does MX matter for cold email?
Your own domain needs an MX record so replies to your campaigns can arrive. And before sending to a domain, its MX records confirm it can actually receive mail and reveal its provider. A missing MX is a red flag that the address will bounce.
Is the MX lookup free?
Yes. It is free and unlimited, with no signup. It runs on our server against live DNS and keeps nothing you type.
What do the priority numbers on MX records mean?
The number is a preference value, and lower wins. Sending servers try the MX with the lowest number first and only fall back to higher numbers if it's unreachable, so the lowest-numbered host is the primary mail server. Records that share the same number are used interchangeably to balance the load.
How can I tell if a domain uses Google Workspace or Microsoft 365?
Look at the MX hostname. Google Workspace domains point at smtp.google.com or aspmx.l.google.com and its alt hosts, while Microsoft 365 domains point at a tenant name ending in mail.protection.outlook.com. If you instead see pphosted.com, mimecast.com or similar, a security gateway is filtering the mail before it reaches the real provider behind it.
What happens if a domain has no MX record?
In most cases mail to that domain bounces, because there's no server advertised to receive it. A sender can technically fall back to the domain's A record when no MX exists, but you shouldn't count on it. A single MX pointing to a bare dot is a null MX, which explicitly declares that the domain never accepts email.
Do MX records affect email deliverability?
MX records control where email is routed, not whether it lands in the inbox. Your deliverability depends on your own domain's SPF, DKIM and DMARC setup, your sending reputation and your content. That is why this check runs those four other checks with the MX lookup.
How long do MX record changes take to take effect?
MX changes propagate according to the record's TTL, commonly between 5 minutes and an hour. Resolvers that already cached the old record keep using it until that TTL expires, so lowering the TTL a day before a migration makes the cutover much faster.
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