The Lupaxa SRE Toolbox
Part of The Lupaxa Project

lupaxa-smtp-tester

Send a test email through an SMTP server to verify delivery.

Features

• Open one SMTP session and send a short plain-text test message
• Add Date and Message-ID headers automatically
• Require STARTTLS before AUTH or DATA (fail if it is not advertised)
• --tls for implicit TLS (SMTP_SSL, typically port 465)
• --no-starttls to send without the upgrade (plaintext AUTH if used)
• Optional AUTH: username and password together, or omit both
• Credentials from flags or SMTP_USERNAME / SMTP_PASSWORD
• --timeout to bound the socket
• --verbose logs steps without protocol payloads or the password
• Library API (send_test_message, SmtpTestResult with smtp_code)
• Fully typed, linted, formatted, and tested
• No runtime dependencies beyond the standard library

Installation

From PyPI

pip install lupaxa-smtp-tester

From source (development mode)

pip install -e ".[dev]"

Requires Python 3.13+. No runtime dependencies.

Library quick start

from lupaxa.smtp_tester import send_test_message

result = send_test_message(
    "smtp.example.com",
    587,
    "USER",
    "PASS",
    "from@example.com",
    "to@example.com",
)
print(result.ok, result.detail, result.smtp_code)

CLI quick start

smtp-tester --help
smtp-tester --from-address from@example.com --to-address to@example.com \
  --smtp-username USER --smtp-password PASS \
  --smtp-server smtp.example.com --smtp-port 587
smtp-tester -f from@example.com -t to@example.com \
  -s smtp.internal.example.com --no-starttls
smtp-tester -f from@example.com -t to@example.com -u USER \
  -s smtp.example.com --tls -P 465

You can also run the CLI as a module:

python -m lupaxa.smtp_tester --help
python -m lupaxa.smtp_tester --version

Documentation

Online documentation:

Documentation

Source repository:

GitHub

Serve docs locally

From a clone of the repository:

make mkdocs-serve

Then open the local URL printed by MkDocs in your browser.

Development

Clone the repository and install with Make:

make init                # first-time makefile-skills checkout
make python-install-dev  # editable install with [dev]
make python-check        # lint, type-check, and test