OpenVerify MCP

Free, open-source, self-hosted email verification MCP server for local validation, bounded bulk CSV processing, DNS/MX checks, and disposable-email detection — without paid API credits.

Repository: eneelkant/email-validation-tool
License: GPL-3.0

What it does

Important: valid_domain means the domain looks mail-capable. It does not mean the individual mailbox was confirmed.

Related MCP server: Email Verification MCP Server

Requirements

• Node.js 22+

• Optional: Docker

Quick start (STDIO)

npm install
npm run build
node dist/index.js --transport stdio

Point your MCP client at that command (see Client setup).

Quick start (HTTP)

cp .env.example .env
# Loopback (default OPENVERIFY_HTTP_HOST=127.0.0.1): token optional
# Non-loopback (e.g. 0.0.0.0): OPENVERIFY_HTTP_AUTH_TOKEN is mandatory or startup fails
npm run build
node dist/index.js --transport http

Endpoints:

• MCP: POST /mcp (Streamable HTTP) — Bearer auth when token configured / required

• GET /health, GET /ready, GET /version — liveness only; no secrets

Remote exposure also needs HTTPS (terminate TLS at a reverse proxy) and a strong token.

Docker

# Required: set a token (Compose fails if OPENVERIFY_HTTP_AUTH_TOKEN is unset)
echo 'OPENVERIFY_HTTP_AUTH_TOKEN=change-me-to-a-long-random-value' >> .env
docker compose up --build

Data persists in the openverify-data volume. Do not bake secrets into the image. Image/compose are provided for deployment convenience; treat remote use as requiring auth + TLS review.

MCP tools

1. verify_email

2. verify_emails_batch

3. verify_csv

4. check_domain

5. get_validation_job

6. cancel_validation_job

7. get_statistics

8. clear_cache

9. update_disposable_domains

Client setup

Examples ship in-repo. Tested in this project’s CI/unit suite for transports and health/auth; end-to-end verification inside each proprietary client UI depends on your local install and that client’s current MCP support — do not assume automatic compatibility.

After npm run build, Cursor/Gemini can use:

{
  "command": "node",
  "args": ["dist/index.js", "--transport", "stdio"]
}

(Use an absolute path in Claude Desktop.)

Configuration

See .env.example. Key variables:

• OPENVERIFY_TRANSPORT — stdio | http | both (STDIO needs no HTTP token)

• OPENVERIFY_HTTP_HOST — default 127.0.0.1 (loopback); 0.0.0.0 requires auth token

• OPENVERIFY_HTTP_AUTH_TOKEN — Bearer for MCP; required for non-loopback HTTP

• OPENVERIFY_CSV_BATCH_SIZE — streaming batch size (default 100, cap 1000)

• OPENVERIFY_MAX_CSV_BYTES — max CSV bytes accepted (default 100 MiB)

• OPENVERIFY_CONCURRENCY — validation concurrency

• OPENVERIFY_SMTP_ENABLED — default false

• OPENVERIFY_LOG_EMAILS — default false (redact emails in logs)

CSV jobs stream in bounded batches (read → parse → batch → validate → ordered write), support cancellation, preserve row order/columns, and sanitize formula-like cells. Cancellation stops new batches, flushes completed output, and marks the job cancelled.

Documentation

• Architecture

• Validation statuses

• Security policy

• Contributing

• Changelog

Development

npm install
npm run typecheck
npm test
npm run build

Benchmarks

Support for large CSVs (1k / 10k / 100k) is implemented via streaming + concurrency. No fabricated throughput numbers are published here — measure on your hardware with verify_csv and report real results if you open a PR.

Security

See SECURITY.md. No paid verification APIs. No automatic CSV uploads. No outbound email.