MX record

An MX record is a DNS entry that tells the rest of the internet which servers are responsible for receiving email on behalf of a domain.

What it is

Every domain that receives mail must publish at least one MX record in DNS. The record tells sending servers where to deliver email addressed to anything@example.com. It is the most fundamental piece of mail routing on the internet: without an MX, a domain simply cannot receive mail.

Each MX record consists of two parts: a priority number and a hostname. The hostname must point to an A or AAAA record (an IP address) — it cannot be a CNAME. The priority is a 16-bit integer where lower means more preferred.

How it works

When a sender wants to deliver mail to alice@example.com, its outgoing server queries DNS for the MX records of example.com. The DNS resolver returns the list, sorted by priority. The sender tries the lowest-priority host first. If that connection fails, it falls back to the next.

When two MX records share a priority, senders are required by RFC to pick between them at random — that's how mail providers spread inbound load across multiple servers. The priority numbers themselves are arbitrary; 10/20/30 is a common convention, but 1, 5, and 12 work equally well.

Common misconfigurations

The single most common MX mistake is pointing the record at a CNAME. RFC 2181 forbids it, and most resolvers will refuse to use the record. The fix is to point the MX directly at the hostname's A record.

Other frequent issues: forgetting to remove old MX records when migrating mail providers (resulting in some mail being delivered to a dead server), publishing an MX that points at a hostname which itself resolves to your sending IP (which fails reverse-DNS checks at many receivers), and forgetting the trailing dot in zone-file syntax — turnmx.google.com into mx.google.com.example.com and mail stops working entirely.

Why it matters for senders

MX records are read more often than you might think. Mailbox providers and anti-abuse services look at the MX of a sender's domain as a coarse trust signal. A domain whose MX is Google Workspace or Microsoft 365 carries different connotations than a domain with no MX at all or an MX pointing at obscure infrastructure.

For cold-email senders, MX configuration also determines whether your replies actually reach you. If you spin up a fresh sending domain and forget to add an MX, every prospect who hits reply gets a bounce. Always ensure inbound routing is working before you run a single warmup cycle.

Related

• SPF — the DNS record for outbound, not inbound
• DKIM — also published in DNS
• Email deliverability — what MX is one ingredient of
• Email warmup guide for 2026
• How NeverSpam verifies your DNS before warmup starts