DNS & Glossary

MX record (Mail Exchange)

The record that routes email: it names the mail servers accepting mail for a domain, with priority values that set primary and backup order.

What it stores

An MX record lists a mail server hostname and a priority number; lower numbers are tried first. Senders resolve the MX records for the recipient's domain, then connect to the lowest-priority host that answers.

ZONE FILE
example.com.   3600   IN   MX   10 mail1.example.com.
example.com.   3600   IN   MX   20 mail2.example.com.

Why it matters

  • Incorrect or missing MX records silently break inbound email for the whole domain.
  • Priority values provide mail failover across multiple servers.

Common mistakes

  • Pointing an MX record at a CNAME (disallowed) instead of a hostname with A/AAAA records.
  • Forgetting to update MX records when switching email providers, bouncing mail.

How WebInspect checks this

  • The Network Inspector reports MX records and analyses the email infrastructure, including SPF, DKIM and DMARC alignment.