How to check if an email address is real or valid using PHP

Is it possible to check if an email is existing similar to this website?

<?php
    if($_POST['email'] != ''){
        // The email to validate
        $email = $_POST['email'];

        // An optional sender
        function domain_exists($email, $record = 'MX'){
            list($user, $domain) = explode('@', $email);
            return checkdnsrr($domain, $record);
        }
        if(domain_exists($email)) {
            echo('This MX records exists; I will accept this email as valid.');
        }
        else {
            echo('No MX record exists;  Invalid email.');
        }
    }
?>
<form method="POST">
    <input type="text" name="email">
    <input type="submit" value="submit">
</form>

This is what I have right now. It checks if the domain exist, but it cannot check if the user's email exist on that domain. Is it possible to do that using PHP?

Mohsen Alizadeh

You should check with SMTP.

That means you have to connect to that email's SMTP server.

After connecting to the SMTP server you should send these commands:

HELO somehostname.com
MAIL FROM: <no-reply@gmail.com>
RCPT TO: <emailtovalidate@domain.com>

If you get "<emailtovalidate@domain.com> Relay access denied" that means this email is Invalid.

There is a simple PHP class. You can use it:

http://www.phpclasses.org/package/6650-PHP-Check-if-an-e-mail-is-valid-using-SMTP.html

You can't verify if an email actually exists without sending an email to that account. But you can verify it's at least formatted like one

if(filter_var($email, FILTER_VALIDATE_EMAIL)) {
    //Email is valid
}

You can add another check if you want. Parse the domain out and then run checkdnsrr

if(checkdnsrr($domain)) {
     // Domain at least has an MX record, necessary to receive email
}

Since people keep downvoting this, here are some notes for you to consider if you're bound and determined to validate email:

Spammers do the connection trick too so don't assume that all servers will respond the same way. One of the other answers links to this library which has this caveat

Some mail servers will silently reject the test message, to prevent spammers from checking against their users' emails and filter the valid emails, so this function might not work properly with all mail servers.

So if there's an invalid address you might not get an invalid address response. The top upvoted answer doesn't mention this.
Spam lists. Yes, you can get blacklisted trying to do this (remember I said spammers know these tricks too). They blacklist by IP address and if your server is constantly doing verification connections you run the risk of winding up on Spamhaus or another block list. If you get blacklisted, what good does it do you to validate the email address?
If it's really that important to verify an email address the accepted way is to force the user to respond to an email. Send them a full email with a link they have to click to be verified. It's not spammy, and you still get to verify if it's valid.

I have been searching for this same answer all morning and have pretty much found out that it's probably impossible to verify if every email address you ever need to check actually exists at the time you need to verify it. So as a work around, I kind of created a simple PHP script to verify that the email address is formatted correct and it also verifies that the domain name used is correct as well.

GitHub here https://github.com/DukeOfMarshall/PHP---JSON-Email-Verification/tree/master

<?php

# What to do if the class is being called directly and not being included in a script     via PHP
# This allows the class/script to be called via other methods like JavaScript

if(basename(__FILE__) == basename($_SERVER["SCRIPT_FILENAME"])){
$return_array = array();

if($_GET['address_to_verify'] == '' || !isset($_GET['address_to_verify'])){
    $return_array['error']              = 1;
    $return_array['message']            = 'No email address was submitted for verification';
    $return_array['domain_verified']    = 0;
    $return_array['format_verified']    = 0;
}else{
    $verify = new EmailVerify();

    if($verify->verify_formatting($_GET['address_to_verify'])){
        $return_array['format_verified']    = 1;

        if($verify->verify_domain($_GET['address_to_verify'])){
            $return_array['error']              = 0;
            $return_array['domain_verified']    = 1;
            $return_array['message']            = 'Formatting and domain have been verified';
        }else{
            $return_array['error']              = 1;
            $return_array['domain_verified']    = 0;
            $return_array['message']            = 'Formatting was verified, but verification of the domain has failed';
        }
    }else{
        $return_array['error']              = 1;
        $return_array['domain_verified']    = 0;
        $return_array['format_verified']    = 0;
        $return_array['message']            = 'Email was not formatted correctly';
    }
}

echo json_encode($return_array);

exit();
}

class EmailVerify {
public function __construct(){

}

public function verify_domain($address_to_verify){
    // an optional sender  
    $record = 'MX';
    list($user, $domain) = explode('@', $address_to_verify);
    return checkdnsrr($domain, $record);
}

public function verify_formatting($address_to_verify){
    if(strstr($address_to_verify, "@") == FALSE){
        return false;
    }else{
        list($user, $domain) = explode('@', $address_to_verify);

        if(strstr($domain, '.') == FALSE){
            return false;
        }else{
            return true;
        }
    }
    }
}
?>

You should check if the email has MX record. Zend-Framwork's filter component has the methods to validate email against MX record.

I have come across EmailPie

https://github.com/apilayer/emailpie, which requires this installation:

Make sure redis is installed and running on the standard ports!

git clone git@github.com:bryanhelmig/emailpie.git
cd emailpie
mkvirtualenv emailpie
pip install -r requirements
python rundev.py
Visit http://localhost:5000/v1/check?email=test@gmail.com

来源：https://stackoverflow.com/questions/19261987/how-to-check-if-an-email-address-is-real-or-valid-using-php

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