MX record lookup

MX records tell senders where to deliver mail for a domain. Each MX has a preference value — lower numbers tried first, ties broken randomly. Use to verify mail routing or diagnose delivery failures.

beginner MX

How to look it up

Four ways to query — pick by what's available on your machine.

digdig MX example.com +short

hosthost -t MX example.com

nslookupnslookup -type=MX example.com

dotdigdotdig mx example.com

Sample response

10 mx1.example.com.
10 mx2.example.com.
20 backup-mx.example.com.

Format

Format: `<preference> <hostname>.`. Lower preference is preferred. The trailing dot is part of the FQDN.

Common pitfalls

MX records MUST point to A/AAAA records, NOT CNAMEs (RFC 2181). Mailers may reject CNAME-pointed MX.
Multiple MX with same preference = round-robin between them. To prefer one mailer, give it the lowest preference value.
Missing MX → mail delivery falls back to the A record of the domain itself (RFC 5321 §5.1). Most operators turn this off explicitly with `0 .` 'null MX' record.

Why it matters for security

security relevance MX records expose your mail infrastructure — attackers use them to identify mail providers and craft spoofing campaigns. Pair with SPF/DKIM/DMARC.

Use cases

Diagnose 'mail not arriving' complaints
Verify MX after switching providers
Check for backup MX before failover testing
Audit external mail flow

Look up DNS without flag soup

dotdig is a friendly DNS resolver — formatted output, custom resolver support, DNSSEC validation. Zero-config alternative to dig.

Open dotdig

Related DNS lookups

NS · TXT · PTR · CNAME · ↗ validate emails before MX lookup