What is a sending node or data center?
A sending node or data center is a location containing email sending infrastructure: servers, network equipment, IP addresses, and supporting systems.
What's in a sending node:
- MTA servers: The machines that actually send email
- Queue servers: Holding pending messages for delivery
- Network infrastructure: Routers, switches, bandwidth
- IP address blocks: The addresses used for sending
- Storage: Logs, queued messages, local caches
Why multiple locations:
Reduced latency: Sending from Europe to European mailbox providers is faster than from the US
- Redundancy: If one data center fails, others continue operating
- Capacity distribution: Spread load across locations
- Data residency: Some regulations require data processing in specific regions
- IP diversity: Different IP ranges from different network providers
Large ESPs operate nodes across North America, Europe, Asia Pacific, and sometimes South America. Traffic routes to appropriate nodes based on destination, load, and health.
When an ESP mentions "global infrastructure," they're referring to this distributed network of sending nodes working together as a unified platform.
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