How to correlate ESP logs with Postmaster data?

Combining your ESP's delivery logs with mailbox provider data from Postmaster Tools provides fuller insight into deliverability issues.

• What ESP logs show:
• Your perspective: what you sent, when, delivery status
• Per-message detail
• Error codes and messages from receiving servers
• Campaign and recipient-level data
• What Postmaster Tools show:
• Provider's perspective: how they view your sending
• Reputation scores
• Spam rates (complaints)
• Authentication results aggregated
• Delivery errors from their side
• Correlation approach:

1. Identify the time period of concern in your ESP
2. Check Postmaster data for the same period
3. Look for correlated patterns:

• ESP shows delivery drops to Gmail → Postmaster shows reputation decline
• ESP shows deferrals → Postmaster shows delivery errors
• ESP shows normal delivery → Postmaster shows spam rate spike (spam folder delivery)
• Common correlations:
• Reputation drop in Postmaster often precedes delivery issues in ESP logs
• Spam rate increases explain inbox placement changes
• Authentication failures in Postmaster explain rejection patterns

Postmaster data is domain-level; ESP logs are message-level. Use Postmaster to understand the "why" behind patterns you see in ESP logs.