This is open-source, but I also offer a SaaS solution that has check-if-email-exists packaged in a nice friendly web interface. If you are interested, find out more at Reacher. If you have any questions, you can contact me at [email protected].

3 non-SaaS ways to get started with check-if-email-exists.

This option allows you to run a HTTP backend using Docker 🐳, on a cloud instance or your own server. Please note that outbound port 25 must be open.

docker run -p 8080:8080 reacherhq/backend:latest

Then send a POST http://localhost:8080/v0/check_email request with the following body:

{
    "to_email": "[email protected]",
    "from_email": "[email protected]", // (optional) email to use in the `FROM` SMTP command, defaults to "[email protected]"
    "hello_name": "my-server.com",    // (optional) name to use in the `EHLO` SMTP command, defaults to "localhost"
    "proxy": {                        // (optional) SOCK5 proxy to run the verification through, default is empty
        "host": "my-proxy.io",
        "port": 1080,
        "username": "me",             // (optional) Proxy username
        "password": "pass"            // (optional) Proxy password
    },
    "smtp_port": 587                  // (optional) SMTP port to do the email verification, defaults to 25
}

Note: The CLI binary doesn't connect to any backend, it checks the email directly from your computer.

Head to the releases page and download the binary for your platform.

> $ check_if_email_exists --help
check_if_email_exists 0.9.1
Check if an email address exists without sending an email.

USAGE:
    check_if_email_exists [FLAGS] [OPTIONS] [TO_EMAIL]

Check out the dedicated README.md for all options and flags.

In your own Rust project, you can add check-if-email-exists in your Cargo.toml:

[dependencies]
check-if-email-exists = "0.9"

And use it in your code as follows:

use check_if_email_exists::{check_email, CheckEmailInput, CheckEmailInputProxy};

async fn check() {
    // Let's say we want to test the deliverability of [email protected].
    let mut input = CheckEmailInput::new(vec!["[email protected]".into()]);

    // Verify this email, using async/await syntax.
    let result = check_email(&input).await;

    // `result` is a `Vec<CheckEmailOutput>`, where the CheckEmailOutput
    // struct contains all information about our email.
    println!("{:?}", result);
}

The reference docs are hosted on docs.rs.

The output will be a JSON with the below format, the fields should be self-explanatory. For [email protected] (note that it is disabled by Gmail), here's the exact output:

{
	"input": "[email protected]",
	"is_reachable": "invalid",
	"misc": {
		"is_disposable": false,
		"is_role_account": false
	},
	"mx": {
		"accepts_mail": true,
		"records": [
			"alt3.gmail-smtp-in.l.google.com.",
			"gmail-smtp-in.l.google.com.",
			"alt1.gmail-smtp-in.l.google.com.",
			"alt4.gmail-smtp-in.l.google.com.",
			"alt2.gmail-smtp-in.l.google.com."
		]
	},
	"smtp": {
		"can_connect_smtp": true,
		"has_full_inbox": false,
		"is_catch_all": false,
		"is_deliverable": false,
		"is_disabled": true
	},
	"syntax": {
		"domain": "gmail.com",
		"is_valid_syntax": true,
		"username": "someone",
		"suggestion": null
	}
}

Many online services (https://hunter.io, https://verify-email.org, https://email-checker.net) offer this service for a paid fee. Here is an open-source alternative to those tools.

check-if-email-exists's source code is provided under a dual license model.

If you want to use check-if-email-exists to develop commercial sites, tools, and applications, the Commercial License is the appropriate license. With this option, your source code is kept proprietary. Purchase a check-if-email-exists Commercial License at https://reacher.email/pricing.

If you are creating an open-source application under a license compatible with the GNU Affero GPL license v3, you may use check-if-email-exists under the terms of the AGPL-3.0.

➡️ Read more about Reacher's license.

This means that the server does not allow real-time verification of an email right now. It may happen for multiple reasons: your IP is blacklisted, the SMTP port 25 is blocked, the email account is momentarily receiving too many emails (spam protection)... or the email provider simply does not allow real-time verification at all. The details of this "unknown" case can be found in the smtp.error and mx.error fields.

Most ISPs block outgoing SMTP requests through port 25, to prevent spam. check-if-email-exists needs to have this port open to make a connection to the email's SMTP server, so won't work behind these ISPs, and will instead hang until it times out. There's unfortunately no easy workaround for this problem, see for example this StackOverflow thread. One solution is to rent a Linux cloud server with a static IP and no blocked ports, see for example our Self-Host Guide for which cloud providers open port 25.

To see in detail what the binary is doing behind the scenes, run it in verbose mode with RUST_LOG=debug to see the logs.

Feel free to check out Reacher's FAQ.

Build the CLI from source or the HTTP backend from source.