What’s the difference between SMTP transcript vs event log?

SMTP transcripts and event logs capture delivery information at different levels of detail.

SMTP transcript:

Raw protocol conversation between servers

Shows every command and response

Includes EHLO handshake, authentication, DATA transmission

Contains exact error messages from receiving server

Example snippet:

250-mail.example.com Hello

250-PIPELINING

250 OK

RCPT TO:<user@example.com>

550 User not found

Event log:

High-level record of what happened

Standardized events: sent, delivered, bounced, deferred, opened, clicked

Timestamps and basic metadata

Aggregated and normalized across many deliveries

Example: "Message abc123 bounced at 2026-02-05 10:30:00 - User unknown"

When to use which:

Event logs: Normal monitoring, reporting, automation triggers, general troubleshooting

SMTP transcripts: Deep debugging when event logs don't explain the problem, understanding exact rejection reasons, diagnosing unusual server behavior

ESPs typically provide event logs through dashboards and APIs. SMTP transcripts may require special access or support requests. Self-hosted MTAs can log full transcripts if configured.