A minimal SMTP sink for local testing. It receives emails via SMTP and exposes them via an HTTP endpoint for inspection.

• Default HTTP endpoint: http://localhost:1080/emails
• Default SMTP port: 1025

Example response from GET /emails:

[
  {
    "id": "1712345678901-abc123",
    "to": ["bob@example.com"],
    "from": "alice@example.com",
    "subject": "Hello",
    "text": "Hi Bob!",
    "date": "2025-01-01T12:34:56.000Z",
    "headers": {"subject": "Subject: Hello"}
  }
]

npm install

• Dev (no build):

npm run dev -- --smtpPort 1025 --httpPort 1080 --max 10 --whitelist bob@example.com,alice@example.com

• Build and run:

npm run build
npm start -- --smtpPort 1025 --httpPort 1080

• Docker (local):

npm run docker:build
npm run docker:run
# Or directly
# docker run --rm -p 1025:1025 -p 1080:1080 smtp-sink:dev --smtpPort 1025 --httpPort 1080

• Optional global install (publishing flow):

npm install -g smtp-sink
smtp-sink --smtpPort 1025 --httpPort 1080

• -s, --smtpPort SMTP port to listen on (default 1025)
• -h, --httpPort HTTP port to listen on (default 1080)
• -w, --whitelist Comma-separated allowed sender addresses (MAIL FROM). Empty = allow all
• -m, --max Max number of emails to retain in memory (default 10)

• UI: open http://localhost:1080/ to view emails (auto-refresh)
• GET /emails: returns JSON array of recent emails
• DELETE /emails: clears stored emails (204 No Content)

Enable TLS for SMTP. You can supply your own key/cert or generate self-signed automatically.

• Self-signed for local testing:

npm run dev -- --tls --tlsSelfSigned

• Provide key/cert files:

npm run dev -- --tls --tlsKey ./certs/key.pem --tlsCert ./certs/cert.pem

You can use any SMTP client. For example with Python or swaks; or a raw TCP session:

$ nc 127.0.0.1 1025
220 localhost ESMTP
HELO localhost
250 Hello localhost
MAIL FROM:<alice@example.com>
250 OK
RCPT TO:<bob@example.com>
250 OK
DATA
354 End data with <CR><LF>.<CR><LF>
Subject: Hello

Hi Bob!
.
250 OK: queued
QUIT
221 Bye

MIT