A Minimal Approach to Check Non Existing Mail.

In the following function, the code first performs basic email validations and then checks whether the domain of each email has a valid MX record. This helps verify if the email address belongs to a real mail server or is likely fake. To perform this verification, we use PHP’s built-in checkdnsrr() function, whose syntax is:

checkdnsrr(string $hostname, string $type = "MX"): bool

This function returns a boolean value:

• The first parameter ($hostname) is the domain name as a string.
• The second parameter ($type) is optional and specifies the DNS record type to check (default is "MX").

Here’s a working example that filters out invalid or fake email addresses from an array:

<?php
$emails = [
    '[email protected]',
    'bademail@',
    '[email protected]',
    '[email protected]'
];

function filter_spam_emails(array $emails): array {
    $valid = [];

    foreach ($emails as $email) {
        $email = trim($email);

        // Validate email format
        if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
            continue;
        }

        // Extract the domain from the email
        $domain = strtolower(substr(strrchr($email, "@"), 1));

        // Check if the domain has an MX record (indicating a real mail server)
        if (!checkdnsrr($domain, "MX")) {
            continue;
        }

        $valid[] = $email;
    }

    return $valid;
}

$clean = filter_spam_emails($emails);

echo "<pre>";
print_r($clean);

Summary:
This script efficiently filters a list of email addresses by validating their syntax and verifying that their domains have MX records. It’s a simple yet effective way to reduce spam or invalid entries when processing user-submitted emails in PHP.