MX lookup: check mail server recordsMX lookup
Shows which servers receive email for your domain, in priority order, with each server's address, reverse DNS and provider.
What this check looks at
- MX records and their priorities
- IPv4/IPv6 addresses of each mail server
- Reverse DNS (PTR) and provider
- MX pointing to a CNAME or an IP
- Null MX and domains without MX
What it reads and what it doesn't
DNS only: the MX records, each mail server's A/AAAA and CNAME records, and the reverse DNS (PTR) of its first IPv4 address. No connection is made to the mail server and no email is sent.
What is an MX record?
An MX (Mail Exchanger) record tells the world which server receives email for your domain. Every MX record has a priority: senders try the lowest number first and fall back to the next if it's unreachable. An MX record must point to a hostname. One that points to an IP address or to a CNAME alias breaks the rules, and some senders won't deliver to it.
DNS only: the MX records, each mail server's A/AAAA and CNAME records, and the reverse DNS (PTR) of its first IPv4 address. No connection is made to the mail server and no email is sent.
How to read the result
- Priority
- Lower numbers are tried first. With priorities 10 and 20, the 20 server is the backup. Servers with equal priority share the load.
- Reverse DNS (PTR)
- The record that maps an IP back to a name. Not required for receiving mail; if the same server also sends mail, receivers expect a PTR that matches its name.
- Null MX
- A single record with priority 0 and target "." says the domain accepts no email (RFC 7505). The right setting for web-only domains.
- No MX
- Senders fall back to the domain's A record. Usually that's unintended: if your web server doesn't accept mail, messages bounce.
Common problems and how to fix them
Every issue this check can flag, why it matters and what to change in DNS.
No MX record
Why it matters: Without an MX, senders try to deliver to your web server. If it doesn't accept mail, messages bounce after a delay.
What to do: If you use email, add your provider's MX records. If you don't, publish a null MX so senders fail fast.
example.com. MX 0 .MX points to a CNAME
Why it matters: RFC 2181 forbids an MX target from being an alias. Most senders still deliver, some refuse, so delivery isn't guaranteed.
What to do: Point the MX record at the real server name the CNAME resolves to.
IP address in MX
Why it matters: An MX record only takes a hostname. A record with an IP address is invalid and mail can't be delivered.
What to do: Give the server a name (for example mail.example.com A 203.0.113.10) and use that name in the MX.
mail.example.com. A 203.0.113.10example.com. MX 10 mail.example.com.Mail server doesn't resolve
Why it matters: The server has no A or AAAA record, so senders can't deliver to this MX. Usually it's left over from a provider you stopped using.
What to do: Delete the unused MX record or fix the server name's A record.
Null MX
Why it matters: The domain states that it accepts no email. If that's deliberate, it's correct.
What to do: If you want to receive mail on this domain, remove the null MX and add your provider's MX records.
No reverse DNS
Why it matters: Not needed for receiving mail. If the same server also sends mail, receivers may treat mail from a server without a PTR as spam.
What to do: If the server sends mail, ask whoever owns the IP address (your hosting provider) to set its PTR to the server's name.
Frequently asked questions
- How do I look up MX records?
- Enter your domain above. The lookup lists MX records by priority with each server's IP address and provider. On the command line, dig MX example.com or nslookup -type=mx example.com shows the same records.
- What does MX priority mean?
- A sending server tries the MX with the lowest priority value first. With priorities 10 and 20, the 20 server is only used when 10 can't be reached. What matters is the order, not the number itself.
- How long does an MX change take to apply?
- As long as the record's TTL: with a TTL of 3600, within an hour at most. Lowering the TTL before the change speeds up the switch. Keep the old server running for a while during the move.
- Can my website and email be with different companies?
- Yes. The website is routed by the A record and email by the MX record, independently of each other. You can host the site with one company and keep email on Google Workspace or Microsoft 365.
Primary sources
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Each one answers a single question about a single record. No account needed.
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To see every check in one report:Email security check