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.