MX Lookup
Look up a domain's mail servers, sorted by priority, with their IP addresses and reverse DNS.
What is an MX record?
An MX (Mail Exchanger) record tells the rest of the internet which servers accept email for your domain. When someone sends mail to [email protected], the sending server looks up your domain's MX records and delivers to the listed mail server.
A domain can have several MX records. Each carries a priority number — lower numbers are tried first. Equal priorities are load-balanced. Secondary MX records with higher numbers act as backups if the primary is unreachable.
What this tool shows
- Every MX record, sorted by priority (the order mail servers actually try them)
- The IP address(es) each mail server hostname resolves to
- The reverse DNS (PTR) name for each IP — relevant to deliverability
- The mail provider detected from the MX hostnames (Google Workspace, Microsoft 365, etc.)
Reading MX priorities
Priority is about order, not importance — a lower number means "try me first." Google Workspace, for example, publishes one MX at priority 1 and several at 5/10 as fallbacks. The absolute values don't matter; only their relative order does. 1 and 10 behave identically to 10 and 20.
Common MX problems
No MX records
If a domain has no MX records, most senders fall back to the domain's A record — but many won't, and the domain effectively can't receive mail reliably. If you expect to receive email, you need at least one MX record.
MX pointing at a CNAME
An MX record must point at a hostname that has an A/AAAA record, not at a CNAME. Pointing MX at a CNAME violates RFC 2181 and some servers will reject it.
MX hostname with no IP
If a mail server hostname doesn't resolve to an IP, mail can't be delivered to it. This tool flags any MX hostname that fails to resolve.
Frequently Asked Questions
What does the priority number mean?
It's the order in which sending servers try your mail servers — lowest first. Only the relative order matters, not the absolute value. Equal priorities are used in a roughly round-robin fashion for load balancing.
How many MX records should I have?
At least one. Most managed providers publish several automatically for redundancy — you don't need to add backups yourself. If you self-host, a secondary MX at a higher priority number gives you a fallback when the primary is down.
How long do MX changes take to propagate?
It depends on the TTL of your existing MX records — usually anywhere from 5 minutes to a few hours. Lower the TTL a day before a planned migration so the switch is fast.
Why does my MX point at a different domain?
That's normal and expected when you use a hosted mail provider. Google Workspace MX points at aspmx.l.google.com, Microsoft 365 at *.mail.protection.outlook.com. You're delegating mail handling to their infrastructure.
Can I have no MX record and still send email?
Yes — MX records govern incoming mail. You can send email from a domain with no MX record. But you won't reliably receive replies, and a missing MX can hurt your sending reputation with some receivers.