whmcsZimbraSingle/zimbraAddressAvailable.php

<?php
$allowed_host = 'admin.seecure.ch';
$host = parse_url($_SERVER['HTTP_REFERER'], PHP_URL_HOST);
if(substr($host, 0 - strlen($allowed_host)) != $allowed_host) {
  die("This file cannot be accessed directly");
}

use WHMCS\Database\Capsule;
define("CLIENTAREA", true);
require_once(__DIR__ . '/../../../init.php');
require_once(ROOTDIR . '/includes/dbfunctions.php');
require_once dirname(__FILE__) . '/zimbraSingle.inc';

$whmcs = App::self();
$productID = $_GET['pid'];
$accessData = array('zimbraServer' => '', 'adminUser' => '', 'adminPass' => '');
$serverIDObj = Capsule::table('tblhosting')
	->select('server')
	->where('id', '=', $productID)
	->get();
$serverID = $serverIDObj[0]->server;
$server = Capsule::table('tblservers')
	->select('ipaddress', 'username', 'password')
	->where('id', '=', $serverID)
	->where('active', '=', 1)
	->get();
$accessData['zimbraServer'] = $server[0]->ipaddress;
$accessData['adminUser'] = $server[0]->username;
$adminPassCrypt = $server[0]->password;
$adminPassDecrypt = localAPI('DecryptPassword', array('password2' => $adminPassCrypt));
if ($adminPassDecrypt['result'] == 'success') {
	$accessData['adminPass'] = $adminPassDecrypt['password'];
}
$api = new Zm_Auth($accessData['zimbraServer'], $accessData['adminUser'], $accessData['adminPass'], "admin");
$login = $api->login();
if(is_a($login, "Exception")) {
	logModuleCall(
		'zimbrasingle',
		__FUNCTION__,
		$accessData,
		"Error : cannot login to " . $accessData['zimbraServer'],
		$serverID
	);
	exit();
} else {
	$apiAccountManager = new Zm_Account($api);
		if( $apiAccountManager->accountExists($account_name)) {
		echo 'no';
	} else {
		echo 'yes';
	}
}