Glossary
MX record
An MX (mail exchanger) record is a DNS record that names the mail servers accepting email for a domain, each with a priority number. Sending servers look it up to find where to deliver mail addressed to that domain.
What Is MX Record?
In short An MX record has a preference number and a hostname: example.com MX 10 mx1.mailhost.com.
Senders try the lowest number first, and records with equal numbers share the load. The target must be a hostname with its own A or AAAA record. RFC 2181 forbids pointing an MX at a CNAME alias. If a domain has no MX record at all, senders fall back to its address record, which RFC 5321 calls an implicit MX.
MX records control inbound mail only. Which servers may send for you is SPF's job. They still matter for outbound: a sending domain without working MX records can't receive replies or bounce messages, and email verification tools start every check by looking up the domain's MX.
MX Record Example
Example: a team sets up a new sending domain on Google Workspace and adds one MX record, smtp.google.com, priority 1. Without it, prospects who reply to the first campaign would get a bounce back, and the team would never see those replies.
MX Record in Practice
Mailbox providers publish the values to use. Google Workspace, for example, now uses a single MX record, smtp.google.com with priority 1, and still supports the older aspmx records on domains set up before 2023.
FAQ
What is an MX record?
A DNS record that tells other mail servers where to deliver email for your domain. It holds a priority number and the hostname of a mail server.
What does MX priority mean?
The number before the hostname. RFC 5321 says lower numbers are more preferred, so senders try the lowest first and move to higher ones if it fails. Records with the same number share the load.
What happens if a domain has no MX record?
Senders fall back to the domain's own address record, which RFC 5321 treats as an implicit MX. If there is no address record either, mail to the domain cannot be delivered.
Can an MX record point to a CNAME?
No. RFC 2181 says the name in an MX record must not be an alias. Point it to a hostname that has its own A or AAAA record.
What MX record does Google Workspace use?
Google tells new domains to use one MX record, smtp.google.com with priority 1. Domains set up before 2023 may still use the older aspmx values, which Google continues to support.
Do This in Ken
Do This in Ken
Delivery handles DNS setup for the domains it provisions and checks MX on each one, so replies reach the mailbox and show up in Inbox.
- Module
- Delivery
- Open in Ken
- /features
The new Ken opens to the waiting list in batches.
Related
- GTM Glossary
Every GTM term, grouped by topic.
- SPF (Sender Policy Framework)
- CNAME record
- PTR record
- Email verification
- DKIM (DomainKeys Identified Mail)
- Ken
Sources
| Source | Checked |
|---|---|
| RFC 5321: Simple Mail Transfer Protocol | |
| RFC 2181: Clarifications to the DNS Specification | |
| Google Workspace Admin Help: Set up MX records for Google Workspace |
Changelog
- Page published.