MX Lookup
See the MX records of any domain by priority, their IP addresses and common misconfigurations (CNAME targets, unresolvable hosts, null MX).
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What this checks
Lists the mail exchangers for the domain in priority order and resolves each to IPv4/IPv6.
Flags MX targets that are CNAMEs or do not resolve.
If it fails
- No MX: mail is delivered to the domain's A record instead; publish MX records or a null MX.
- Unresolvable host: fix the A/AAAA record of the MX hostname.
FAQ
Lower or higher priority first?
Lower number = higher priority. Senders try the lowest first.
Can an MX point to an IP address?
No. MX must point to a hostname that has A/AAAA records.
What is a null MX?
A single MX record "0 ." declaring the domain does not accept email (RFC 7505).
Why only one MX?
It works, but a second host adds failover when the first is down.
Guides
DNS record types explained: A, MX, TXT, CNAME and moreMX record points to a CNAME: why it breaks and the fixMX host does not resolve: causes and how to fix itNull MX (RFC 7505): publish it for domains with no mailReverse DNS (PTR) for mail servers: how to set itHow to set up MX records (priorities, null MX, migration)Set up SPF, DKIM and DMARC for Google WorkspaceSet up SPF, DKIM and DMARC for Microsoft 365Set up SPF, DKIM and DMARC for Zoho MailSPF “too many DNS lookups”: why it happens and how to fix it