How do priority levels in MX records work?

MX records include a priority number (also called preference):

Lower number = higher priority: Priority 10 is tried before priority 20.

Delivery attempt order: Senders connect to the lowest priority server first. If it fails, they try the next higher priority.

Equal priorities: Multiple servers with the same priority receive mail in round-robin fashion.

Common configurations:

• Primary server: priority 10
• Backup server: priority 20
• Emergency backup: priority 30

Spam filters often run at lower priority numbers to inspect mail before delivery to the actual mail server.

Docking instructions with preferred berth first, backup berths for when the primary is full or unavailable.