Mail Server Tester

A continuous mail server testing tool that monitors mail delivery between multiple mail servers and exposes metrics for Prometheus monitoring.

Helm Chart Installation

First, add the Helm repository:

helm repo add mail-server-tester https://guided-traffic.github.io/mail-server-tester
helm repo update

Then install the chart:

helm install mail-tester mail-server-tester/mail-server-tester \
  --namespace mail-tester \
  --create-namespace \
  --set config.testserver.smtp_server=smtp.example.com \
  --set config.testserver.smtp_user=user@example.com \
  --set config.testserver.smtp_password=your-password \
  --set config.testserver.imap_server=imap.example.com \
  --set config.testserver.imap_user=user@example.com \
  --set config.testserver.imap_password=your-password

For a complete list of configuration values, check the chart's values.yaml.

Features

• Connection verification: Validates SMTP and IMAP credentials at startup
• Continuous bidirectional mail testing between servers
• Prometheus metrics endpoint for monitoring
• Support for TLS/SSL connections
• Configurable test intervals
• Support for multiple external mail servers
• Docker/Podman containerization support
• Command-line options for configuration and error handling

How it works

The tool performs bidirectional mail tests:

1. Test Server → External Servers: Sends test emails from your main server to external servers
2. External Servers → Test Server: Sends test emails from external servers back to your main server

Each test measures:

• Mail delivery success/failure
• Delivery duration
• Error details (if any)

Installation

Building from source

go mod download
go build -o mail-server-tester .

Using Docker

docker build -t mail-server-tester -f Containerfile .
docker run -v $(pwd)/config.yaml:/root/config.yaml mail-server-tester

Using Podman

podman build -t mail-server-tester .
podman run -v $(pwd)/config.yaml:/root/config.yaml mail-server-tester

Configuration

Create a config.yaml file with your mail server configurations:

interval_minutes: 60  # Test interval in minutes

testserver:
  name: testserver
  smtp_server: smtp.main.example.com
  smtp_port: 587
  smtp_user: user@main.example.com
  smtp_password: password
  imap_server: imap.main.example.com
  imap_port: 993
  imap_user: user@main.example.com
  imap_password: password
  tls: true
  skip_cert_verify: false

external_servers:
  - name: external1
    smtp_server: smtp.ext1.example.com
    smtp_port: 587
    smtp_user: user@ext1.example.com
    smtp_password: password1
    imap_server: imap.ext1.example.com
    imap_port: 993
    imap_user: user@ext1.example.com
    imap_password: password1
    tls: true
    skip_cert_verify: true

  - name: external2
    smtp_server: smtp.ext2.example.com
    smtp_port: 587
    smtp_user: user@ext2.example.com
    smtp_password: password2
    imap_server: imap.ext2.example.com
    imap_port: 993
    imap_user: user@ext2.example.com
    imap_password: password2
    tls: false
    skip_cert_verify: false

Configuration Parameters

Parameter	Description	Default
interval_minutes	Minutes between test cycles	60
name	Server identifier for metrics	-
smtp_server	SMTP server hostname	-
smtp_port	SMTP server port	-
smtp_user	SMTP username	-
smtp_password	SMTP password	-
imap_server	IMAP server hostname	-
imap_port	IMAP server port	-
imap_user	IMAP username	-
imap_password	IMAP password	-
tls	Enable TLS/SSL	false
skip_cert_verify	Skip certificate verification	false

Usage

Command line options

# Show help
./mail-server-tester --help

# Use default config.yaml
./mail-server-tester

# Use custom config file
./mail-server-tester --configpath /path/to/config.yaml

# Exit immediately if connection verification fails
./mail-server-tester --exit-on-connection-error

# Combine options
./mail-server-tester --configpath /path/to/config.yaml --exit-on-connection-error

Available command line options:

• --configpath PATH - Path to configuration file (default: config.yaml)
• --exit-on-connection-error - Exit program if credential verification fails
• --help - Show usage information

Connection Verification

At startup, the application automatically verifies all SMTP and IMAP credentials defined in the configuration. This helps identify configuration issues before starting the main testing loop.

Example output:

=== Überprüfung der Zugangsdaten ===

Teste Testserver 'testserver':
  SMTP (smtp.main.example.com:587)... ✓ OK (0.32s)
  IMAP (imap.main.example.com:993)... ✓ OK (0.28s)

Teste externen Server 'external1':
  SMTP (smtp.ext1.example.com:587)... ✗ FEHLER: SMTP-Authentifizierung fehlgeschlagen (1.20s)
  IMAP (imap.ext1.example.com:993)... ✓ OK (0.45s)

=== Zusammenfassung ===
Erfolgreiche Verbindungen: 3/4
✗ 1 Verbindung(en) fehlgeschlagen!

Running with custom config

./mail-server-tester --configpath /path/to/your/config.yaml

Monitoring

Prometheus Metrics

The application exposes Prometheus metrics on port 8080 at the /metrics endpoint.

Available metrics:

• mail_test_success{from="server1",to="server2"} - Test success (1) or failure (0)
• mail_test_duration_seconds{from="server1",to="server2"} - Test duration in seconds
• mail_test_error_total{from="server1",to="server2"} - Error count per test

Example Prometheus scrape config

scrape_configs:
  - job_name: 'mail-server-tester'
    static_configs:
      - targets: ['localhost:8080']

Dependencies

• Go 1.24+
• github.com/emersion/go-imap - IMAP client
• gopkg.in/yaml.v3 - YAML configuration parsing

License

This project is open source. Please check the repository for license details.