Authoritative MX Record Lookup & Server Inspector
Discover active Mail Exchanger (MX) hosts, priority rankings, IPv4/IPv6 addresses, and Null MX configurations in real-time.
How MX Record Lookup Works
DNS Query Dispatch
Queries authoritative nameservers for resource record type MX (15) across root TLD servers.
Priority Sorting
Parses returned records, sorting by numeric priority preference (lowest integer = highest priority).
Dual-Stack IP Resolution
Resolves A (IPv4) and AAAA (IPv6) records for each host to confirm routability.
RFC Engineering Standards
Every check performed by this tool adheres strictly to the Internet Engineering Task Force (IETF) Request for Comments:
- RFC 5321 (SMTP Architecture)
- RFC 7505 (Null MX Records)
- RFC 1035 (DNS Specification)
Common Issues & How to Fix Them
If our diagnostic discovers configuration anomalies, use the remediation steps below:
Remediation: Domain cannot receive email. Add at least one MX record pointing to your mail provider.
Remediation: The domain explicitly advertises that it does not accept email (`0 .`). Normal for marketing-only domains.
Remediation: The host specified in the MX record cannot be found in DNS. Mail sent to this domain will bounce.
Frequently Asked Questions
What is an MX record and why does priority matter?
A Mail Exchanger (MX) record specifies the mail server responsible for accepting incoming emails on behalf of a domain. The priority value tells sending servers which host to try first (lowest number = highest priority). If the primary host is unreachable, sending MTAs automatically fall back to backup servers.
What happens if a domain has no MX records?
Under RFC 5321, if no MX records exist, sending servers will attempt to deliver directly to the domain's root A record (implicit MX). However, modern ESPs frequently reject or delay mail sent to domains lacking explicit MX records.
What is a Null MX record (RFC 7505)?
A Null MX is a single record configured as `0 .` which explicitly tells sending servers that the domain does not accept email under any circumstances, preventing bounce storms and spoofing attempts.
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