SMTP Test & Generator

Interactive SMTP Tester: Browser cannot open raw TCP sockets to SMTP directly, so this tool generates real-time, copy-ready test commands (cURL, Python, OpenSSL, Node.js) for terminal execution.

Gmail Setup (App Password)
  1. Go to Google Account > Security
  2. Ensure 2-Step Verification is ON
  3. Go to App passwords (or search "App passwords" in account settings)
  4. Enter an app name (e.g. SMTP-Test), click Create
  5. Copy the 16-character password (without spaces) and paste into the Password field below

// Quick Parameter Replacer (Updates test commands below in real-time)

Presets:
1. cURL (Instant Terminal Execution)
2. Python 3 (smtplib - Built-in, No pip install needed)
3. OpenSSL (Test Network & TLS Handshake Connectivity)
4. Node.js (Nodemailer snippet)

Scratchpad

SMTP Standard Ports

Port Protocol / Encryption Usage
587 STARTTLS (Explicit TLS) Recommended modern standard for client-to-server mail submission (Gmail, Outlook)
465 SMTPS (Implicit SSL/TLS) Direct secure socket connection from start (widely used by Gmail, Yahoo)
25 Plain / STARTTLS Server-to-server relay; frequently blocked by ISPs and cloud providers for residential IP
2525 Plain / STARTTLS Alternative submission port when port 587 is blocked

Common SMTP Status Codes

Code Meaning Troubleshooting
220 Service ready Connection established successfully
250 Requested mail action okay, completed Success! Email accepted for delivery
354 Start mail input Server is ready for the body text of email
421 Service not available / Connection closed Rate limit exceeded or IP temporarily throttled
535 Authentication failed Incorrect credentials. For Gmail, you MUST use a 16-char App Password with 2FA ON
550 Mailbox unavailable / Recipient rejected Invalid recipient email address or blocked by spam filter

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