$token = substr( md5( microtime() ), -12 );

$token = base64_encode ( $email ); // The users email will be encoded

$emailToken = base64_decode( $_GET['t'] ); // Contains the users email

if ( base64_encode( base64_decode( $_GET['t'] ) ) === $_GET['t'] ) {
    // Valid base64... we hope but is it a valid email?
    $emailToken = filter_var( base64_decode( $_GET['t'] ), FILTER_SANITIZE_EMAIL );
    if ( filter_var( $emailToken, FILTER_VALIDATE_EMAIL ) ) {
        // Email is valid. Do something to call email info
    }
}