Prometheus metrics

Mailpit includes optional Prometheus metrics support for monitoring mail server performance and usage statistics.

Enabling Prometheus metrics

Prometheus metrics are disabled by default. To enable them, use either the command-line flag or environment variable:

Integrated mode

Serve metrics on the main web UI port, inheriting all configuration such as TLS and authentication, at /metrics:

# Using command line flag
mailpit --enable-prometheus true

# Using environment variable
export MP_ENABLE_PROMETHEUS=true
mailpit

Separate server mode

Run a dedicated metrics server on a custom port without TLS or authentication:

# Custom listen address for separate server
mailpit --enable-prometheus 0.0.0.0:9091

# Using environment variable
export MP_ENABLE_PROMETHEUS="0.0.0.0:9091"
mailpit

Available metrics

Mailpit exposes the following metrics:

Message statistics

  • mailpit_messages (gauge) - Total number of messages in the database
  • mailpit_messages_unread (gauge) - Number of unread messages
  • mailpit_messages_deleted_total (counter) - Total number of messages deleted

SMTP statistics

  • mailpit_smtp_accepted_total (counter) - Total SMTP messages accepted
  • mailpit_smtp_rejected_total (counter) - Total SMTP messages rejected
  • mailpit_smtp_ignored_total (counter) - Total SMTP messages ignored (duplicates)
  • mailpit_smtp_accepted_size_bytes_total (counter) - Total size of accepted SMTP messages in bytes

System statistics

  • mailpit_database_size_bytes (gauge) - Database size in bytes
  • mailpit_uptime_seconds (gauge) - Mailpit uptime in seconds
  • mailpit_memory_usage_bytes (gauge) - Current memory usage in bytes

Tag statistics

  • mailpit_tag_messages (gauge) - Number of messages per tag, labeled by tag name

Prometheus configuration

To configure Prometheus to scrape Mailpit metrics, add the following to your prometheus.yml:

For integrated mode

scrape_configs:
    - job_name: "mailpit"
      static_configs:
          - targets: ["localhost:8025"]
      scrape_interval: 30s
      metrics_path: "/metrics"

For separate server mode

scrape_configs:
    - job_name: "mailpit"
      static_configs:
          - targets: ["localhost:9091"] # Use your custom port
      scrape_interval: 30s
      metrics_path: "/metrics"

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