smtp8

Test any SMTP server in real time — straight from your terminal.

smtp8 connects directly to an SMTP server, streams every protocol event as it happens, and tells you exactly what failed and why. No credentials are stored or logged. No backend required.

Live web app → smtp8.web.app

Requirements

Node 18 or later.

Installation

npm install -g smtp8

Quick start

smtp8

The CLI walks you through each field interactively:

• Host — the SMTP server hostname
• Port — default 587
• Encryption — STARTTLS, SSL/TLS, or NONE
• Username — leave blank to skip AUTH
• Password — leave blank to skip AUTH
• Client name — the EHLO hostname sent to the server (default smtp8.local)

Non-interactive mode

Skip the prompts entirely by passing all values as flags — useful for scripts and CI:

smtp8 test --host smtp.gmail.com
smtp8 test --host smtp.gmail.com --port 465 --encryption SSL_TLS
smtp8 test --host smtp.gmail.com --username [email protected] --password secret

| Flag | Default | |---|---| | --host | required | | --port | 587 / 465 / 25 based on encryption | | --encryption | STARTTLS | | --username | — | | --password | — (prefer SMTP8_PASSWORD env var) | | --client-name | smtp8.local |

Use smtp8 test --help for full usage.

Options

--remote          Route the test through the hosted smtp8 API
--api-url <url>   Route the test through a custom API URL (local or remote)
--version, -v     Print version and exit
--help, -h        Show help and exit

By default, smtp8 runs the SMTP test directly from your machine with no backend. Use --remote or --api-url to route through an API instead.

Configuration

| Source | Description | |---|---| | --api-url <url> | Route through a specific API URL | | --remote | Route through the hosted smtp8 API | | SMTP8_API_URL | Same as --api-url but via environment variable | | SMTP8_PASSWORD | Password for smtp8 test (safer than --password) |

Priority: --api-url → --remote → SMTP8_API_URL → run directly (default).

Examples

# Interactive — runs directly, no backend needed
smtp8

# Non-interactive — test Gmail STARTTLS
smtp8 test --host smtp.gmail.com

# Non-interactive — SSL/TLS on port 465
smtp8 test --host smtp.gmail.com --port 465 --encryption SSL_TLS

# Non-interactive with auth (password via env var)
SMTP8_PASSWORD=secret smtp8 test --host smtp.gmail.com --username [email protected]

# Route through the hosted API
smtp8 --remote
smtp8 test --host smtp.gmail.com --remote

# Route through a custom or local backend
smtp8 --api-url http://localhost:8081
smtp8 test --host smtp.gmail.com --api-url https://api.example.com

Prompt navigation

| Key | Action | |-----|--------| | Tab | Autofill the placeholder value | | Ctrl+C | Go back to the previous field | | Esc | Clear the current field |

Links

• GitHub — source code and issue tracker
• smtp8.web.app — browser version