In simple English
This tool checks if an email address is real and active without sending a message to it. It verifies domain names, tests mail servers, and spots fake or disabled accounts. You can run it on your own server or use it as a command-line utility. It helps you clean your mailing lists before you launch a campaign. The code is free to use under an open-source licence.
What it is
An open-source email verification engine written in Rust that queries mail servers directly. It comes with a Docker-ready HTTP backend and a command-line interface for local checks.
What it is good for
Solo builders who want to verify user sign-ups or clean up contact lists without paying for a commercial email verification service.
- Checks mailboxes directly without sending test emails.
- Runs locally via a command-line tool or on your server with Docker (a way to run a program inside its own sealed box, so it cannot break anything else on your server).
- Provides clean JSON responses for easy integration into your apps.
- Requires port 25 to be open on your server, which many cloud providers block by default.
- High-volume checks need separate SMTP proxy servers to avoid getting your IP address blocked.
- Requires some technical knowledge to set up and operate the Docker container.
Paid email verification services like Hunter or ZeroBounce.
PostgreSQL for storing verification results.
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docker run -p 8080:8080 reacherhq/backend:latest