Examples

Submission on port 587

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

STARTTLS is required. The send fails if the server does not advertise it.

Implicit TLS on port 465

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 465 --tls

Internal relay without AUTH

smtp-tester --from-address from@example.com --to-address to@example.com \
  --smtp-server smtp.internal.example.com --no-starttls

Omit both username and password. --no-starttls is for a plaintext lab or internal relay you already trust.

Credentials from the environment

export SMTP_USERNAME='USER'
export SMTP_PASSWORD='your-smtp-password'
smtp-tester --from-address from@example.com --to-address to@example.com \
  --smtp-server smtp.example.com --smtp-port 587

Amazon SES

smtp-tester --from-address from@example.com --to-address to@example.com \
  --smtp-username AKIAexample --smtp-password SES_SMTP_PASSWORD \
  --smtp-server email-smtp.eu-west-1.amazonaws.com --smtp-port 587

Use an SES SMTP credential, not the AWS access key itself. The From address must be a verified identity in that SES region.

Custom subject and step logs

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 \
  --subject "SMTP probe" --body "ping" --verbose --timeout 15

--verbose prints connect, EHLO, STARTTLS, AUTH, and send. It does not print the password or raw SMTP lines.

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",
    subject="SMTP probe",
    body="ping",
)
print(result.ok, result.detail, result.smtp_code)