If you don't have time to waste configuring, hosting, debugging and maintaining your own email verifier, we offer a SaaS solution that has all of the capabilities check-if-email-exists provides, plus a lot more, and all that 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].

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 an 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.

There are 5 ways you can try check-if-email-exists.

Reacher is a simple SaaS using this library, also open-source!

If you would like a high free tier to test Reacher, consider sponsoring me! You'll get 8000 free email verifications every month, and a this contribution would mean A WHOLE LOT to me.

Reacher provides a fully-fledged REST backend at https://github.com/reacherhq/backend. It is the same backend running for our main product https://reacher.email.

The beckend is built using the fast web framework warp, and exposes an API endpoint for making email verifications.

For an one-click deploy to Heroku, click on the purple Heroku button at reacherhq/backend.

The Docker image is hosted on Docker Hub: https://hub.docker.com/r/reacherhq/check-if-email-exists.

To run it, run the following command:

docker run -p 3000:3000 reacherhq/check-if-email-exists

You can then send a POST request with the following body to http://localhost:3000 to test multiple emails at once:

{
	"to_emails": ["[email protected]"]
}

Here's the equivalent curl command:

curl -X POST -d'{"to_emails":["[email protected]"]}' http://localhost:3000

Optionally, you can also pass in from_email and hello_name fields into the JSON object, see the help message below to understand their meanings.

Note: The 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. Make sure you have openssl installed on your local machine.

> $ check_if_email_exists --help
check_if_email_exists 0.8.22
Check if an email address exists without sending any email.

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

FLAGS:
        --http       Runs a HTTP server.
    -h, --help       Prints help information
    -V, --version    Prints version information

OPTIONS:
        --from-email <FROM_EMAIL>          The email to use in the `MAIL FROM:` SMTP command. [default:
                                           [email protected]]
        --hello-name <HELLO_NAME>          The name to use in the `EHLO:` SMTP command. [default: localhost]
        --http-host <HOST>                 Sets the host IP address on which the HTTP server should bind. Only used when
                                           `--http` flag is on. [default: 127.0.0.1]
        --http-port <PORT>                 Sets the port on which the HTTP server should bind. Only used when `--http`
                                           flag is on. If not set, then it will use $PORT, or default to 3000.
        --proxy-host <PROXY_HOST>          Use the specified SOCKS5 proxy host to perform email verification.
        --proxy-port <PROXY_PORT>          Use the specified SOCKS5 proxy port to perform email verification. Only used
                                           when `--proxy-host` flag is set. [default: 1080]
        --yahoo-use-api <YAHOO_USE_API>    For Yahoo email addresses, use Yahoo's API instead of connecting directly to
                                           their SMTP servers. [default: true]

ARGS:
    <TO_EMAIL>    The email to check.

If you run with the --http flag, check-if-email-exists will serve a HTTP server on http://localhost:3000. You can then send a POST request with the following body to test multiple emails at once:

{
	"to_emails": ["[email protected]"]
}

Here's the equivalent curl command:

curl -X POST -d'{"to_emails":["[email protected]"]}' http://localhost:3000

Optionally, you can also pass in from_email and hello_name fields into the JSON object, see the help message above to understand their meanings.

💡 PRO TIP: To show debug logs when running the binary, run:

RUST_LOG=debug check_if_email_exists [FLAGS] [OPTIONS] [TO_EMAIL]

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

[dependencies]
check-if-email-exists = "0.8"

And use it in your code as follows:

use check_if_email_exists::{check_email, CheckEmailInput};

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

    // Optionally, we can also tweak the configuration parameters used in the
    // verification.
    input
        .from_email("[email protected]".into()) // Used in the `MAIL FROM:` command
        .hello_name("example.org".into()); // Used in the `EHLO` command

    // Verify this input, 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"
	}
}

You can also take a look at the documentation of this JSON object.

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 Deploy to Heroku section.

To see in details what the binary is doing behind the scenes, run it in verbose mode to see the logs.

Feel free to check out Reacher's FAQ.

First, install Rust; you'll need Rust 1.37.0 or later. Then, run the following commands:

# Download the code
$ git clone https://github.com/reacherhq/check-if-email-exists
$ cd check-if-email-exists

# Build in release mode
$ cargo build --release

# Run the binary
$ ./target/release/check_if_email_exists --help

The 1st version of this tool was a simple bash script which made a telnet call. If you would like to use that simpler version, have a look at the legacy branch. The reasons for porting the bash script to the current codebase are explained in issue #4.