An MX record (Mail Exchanger record) is a DNS record that tells other mail servers where to deliver email for your domain. Without correctly configured MX records, email sent to your domain will bounce or be undeliverable.
MX Record Format
example.com. 3600 IN MX 10 mail1.example.com.
example.com. 3600 IN MX 20 mail2.example.com.The number before the mail server hostname is the priority (or preference). Lower numbers = higher priority.
MX Priority and Redundancy
Having multiple MX records with different priorities provides fault tolerance. Sending mail servers try the lowest-priority number first. If that server is unavailable, they try the next highest number (backup MX).
Common MX Configurations
- Google Workspace:
aspmx.l.google.com(priority 1), plus four backup servers - Microsoft 365:
yourdomain-com.mail.protection.outlook.com(priority 0) - Zoho Mail:
mx.zoho.com(priority 10)
Important Rules
- MX records must point to a hostname (A record), never directly to an IP address or CNAME.
- MX records only apply at the domain level — subdomains like
mail.example.comcannot have MX records. - Always configure at least two MX records for redundancy.
Email Authentication
MX records work in tandem with SPF, DKIM and DMARC records to authenticate your email and reduce the risk of spoofing and spam delivery issues.