Usage

The CLI opens one SMTP session and sends a short plain-text message. Short flags match the original script: -f, -t, -u, -p, -s, -P, -T, and -v.

CLI flags

Flag	Default	Description
--from-address	required	From address
--to-address	required	To address
--smtp-username	SMTP_USERNAME	SMTP username; omit with password to skip AUTH
--smtp-password	SMTP_PASSWORD	SMTP password; omit with username to skip AUTH
--smtp-server	required	SMTP hostname
--smtp-port	25	SMTP port
--timeout	10	Socket timeout in seconds
--tls	off	Implicit TLS (SMTP_SSL, typically port 465)
--no-starttls	off	Do not require STARTTLS
--subject	Simple test message	Message subject
--body	built-in body	Plain-text body
--verbose	off	Log SMTP steps without protocol payloads
--version	—	Print the package version and exit

--timeout must be greater than 0. --smtp-port must be an integer from 1 to 65535. Username and password must both be set or both omitted. Flags override SMTP_USERNAME and SMTP_PASSWORD.

STARTTLS is required unless --tls or --no-starttls is set. If STARTTLS is required and the server does not advertise it, the send fails before AUTH. --no-starttls sends in the clear; do not use it with credentials on an untrusted network.

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
smtp-tester --version

A successful send prints email sent to <to-address> and exits 0. A failed send prints a reason on stderr and exits 1. The password is never included in that output or in --verbose logs.

Library

from lupaxa.smtp_tester import send_test_message

result = send_test_message(
    "smtp.example.com",
    587,
    "USER",
    "PASS",
    "from@example.com",
    "to@example.com",
    timeout=10.0,
)
if not result.ok:
    raise SystemExit(f"{result.detail} ({result.smtp_code})")

send_test_message returns an SmtpTestResult with ok, to_address, detail, and smtp_code. Pass use_tls=True for implicit TLS, or starttls=False to skip STARTTLS. Pass None for both username and password to skip AUTH. Invalid port or timeout, or only one credential, raises ValueError.