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 No2Bounce.com. If you have any questions, you can contact me at amaury@reacher.email.

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": "someone@gmail.com",
    "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
    }
}

Note regarding proxy servers It is possible to operate Reacher with your own IP addresses. But if you wish to process more than very small volumes you will need SMTP proxy servers. For SMTP proxy servers please use proxy25.com

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 someone@gmail.com.
    let mut input = CheckEmailInput::new(vec!["someone@gmail.com".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 someone@gmail.com (note that it is disabled by Gmail), here's the exact output:

{
	"input": "someone@gmail.com",
	"is_reachable": "invalid",
	"misc": {
		"is_disposable": false,
		"is_role_account": false,
		"is_b2c": true
	},
	"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 the MIT License.