Glossary / MX record

MX record (mail exchanger)

An MX record (mail exchanger) tells the world which server accepts email for a domain. When someone writes to you@example.com, their mail server checks the MX record for example.com and delivers there. Without MX, mail to the domain never arrives.

An MX record points not to an IP but to a mail server's hostname (like aspmx.l.google.com), which has its own A record. Next to the name sits a number, the priority: the lower it is, the more preferred the server. Backup servers get a higher number and take mail only when the main one is unavailable.

A domain can have several MX records at once, which is how you build redundancy. Email is usually run by a separate provider (Google Workspace, Microsoft 365, a mail host), so MX often points somewhere other than the server that hosts the site.

MX only covers receiving mail. Keeping your outgoing messages out of spam is the job of separate TXT records - SPF, DKIM, and DMARC. So a working MX still does not guarantee your mail gets delivered.

Example

example.com.  3600  IN  MX  10 aspmx.l.google.com.

Common mistakes

• Thinking a higher priority number means a more important server; the lowest number wins.
• Putting an IP address in MX instead of a hostname; MX must reference a host that has its own A record.
• Confusing MX with the site's A record and expecting mail to go where the site is hosted.
• Ignoring SPF, DKIM, and DMARC and then wondering why mail with a valid MX lands in spam.

Related terms

• A record A record (DNS address record)
• AAAA record AAAA record (DNS IPv6 record)
• CNAME record CNAME record (DNS alias)
• TXT record TXT record (DNS text record)
• NS record NS record (name server record)