Владимир

require($_SERVER["DOCUMENT_ROOT"]."/bitrix/modules/main/include/prolog_before.php");

$user_id = 1;

$result = \Bitrix\Main\UserTable::getList(array(
    'select' => array('EMAIL', 'LOGIN', 'NAME', 'LAST_NAME'),
    'filter'  => array('ID' => $user_id),
    'limit' => 1
));

$arUser = $result->fetch();

$post_user = 'login='.$arUser["LOGIN"].'&name='.$arUser["NAME"].'&last_name='.$arUser["LAST_NAME"].'&email='.$arUser["EMAIL"];

$URL = 'https://domain.ru/handlers/file.php';

if( $curl = curl_init() ) {
    curl_setopt($curl, CURLOPT_URL, $URL);
    curl_setopt($curl, CURLOPT_RETURNTRANSFER,true);
    curl_setopt($curl, CURLOPT_POST, true);
    curl_setopt($curl, CURLOPT_POSTFIELDS, $post_user);
    $out = curl_exec($curl);
    curl_close($curl);
}