What are common security risks associated with using PHP scripts for webmail functionality?

Common security risks associated with using PHP scripts for webmail functionality include SQL injection, cross-site scripting (XSS) attacks, and insecure file uploads. To mitigate these risks, it is important to sanitize user inputs, validate uploaded files, and implement proper authentication and authorization mechanisms.

// Example of sanitizing user inputs to prevent SQL injection
$username = mysqli_real_escape_string($conn, $_POST['username']);
$password = mysqli_real_escape_string($conn, $_POST['password']);
$email = filter_var($_POST['email'], FILTER_SANITIZE_EMAIL);