How to integrate custom routing with ESP tracking?

Combining custom mail routing with ESP tracking features requires thoughtful architecture to maintain both control and visibility.

• Approach 1: ESP as smart host
• Your application generates messages
• Messages route through your MTA to ESP
• ESP wraps links, adds tracking pixel, handles analytics
• ESP delivers to recipients
• You get ESP tracking with your origination point
• Approach 2: API injection for tracking only
• Generate content via ESP API to get tracked links/pixels
• Receive the modified content back
• Send through your own MTA
• Track pixels/links point to ESP servers for data collection
• Approach 3: Self-hosted tracking
• Implement your own click/open tracking
• Full control but no ESP features
• Host tracking endpoints on your infrastructure
• Build analytics yourself

Considerations:

• ESP tracking domains need to be trusted (custom tracking domains help)
• Authentication must work for final delivery path
• Reporting may be split between systems
• Cost model changes (may pay for tracking without using ESP delivery)

Some ESPs support these hybrid models better than others. Discuss your architecture with ESP support before committing to a design.