MX (Mail Exchange) records are DNS entries that tell sending mail servers where to deliver email for a domain. Understanding MX records is essential for email deliverability, security, and troubleshooting.
What MX Records Do
When you send email to [email protected], the sending server queries DNS for example.com's MX records. The response lists mail server hostnames that accept email for that domain. Without MX records, email delivery fails (unless an A record fallback exists, which is rare). MX records point to hostnames, not IP addresses—those hostnames have their own A records.
Priority Values
Each MX record has a priority (also called preference) number. Lower numbers indicate higher priority—priority 10 is tried before priority 20. If the primary server is unavailable, senders try backup servers in priority order. Equal priorities mean load balancing—servers are tried randomly. This redundancy ensures email delivery even during outages.
Email Provider Detection
MX records reveal which email service a domain uses. Google Workspace domains point to aspmx.l.google.com, Microsoft 365 uses mail.protection.outlook.com. This information is useful for sales intelligence, competitive analysis, and email deliverability optimization.
Common MX Configurations
Simple setups have one MX record. Enterprise configurations often have multiple records for redundancy: primary, secondary, and sometimes tertiary servers. Cloud email providers (Google, Microsoft) provide their own MX records. Self-hosted email requires configuring MX records to point to your mail server.