What considerations should be made when verifying the syntax and plausibility of email addresses in PHP applications?

When verifying the syntax and plausibility of email addresses in PHP applications, it is important to check for the correct format of an email address (e.g., username@domain.com) using regular expressions. Additionally, you can also validate the domain of the email address by checking for the existence of MX records. This helps ensure that the email address is not only correctly formatted but also points to a valid email server. 

$email = "example@example.com";

// Validate email address format
if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
    // Check MX records for the domain
    list($username, $domain) = explode('@', $email);
    if (checkdnsrr($domain, 'MX')) {
        echo "Email address is valid and has a valid domain.";
    } else {
        echo "Email address has an invalid domain.";
    }
} else {
    echo "Email address has an invalid format.";
}

Keywords

email validation regular expressions filter_var RFC standards domain validation

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