ICalUtil::isMailUser

static function isMailUser($userId): bool
{
	$parameters = [
		'filter' => [
			'ID' => $userId,
		],
		'select' => [
			'ID', 'EXTERNAL_AUTH_ID',
		],
		'limit' => 1,
	];

	$userDd = UserTable::getList($parameters);

	if ($user = $userDd->fetch())
	{
		return $user['EXTERNAL_AUTH_ID'] === 'email';
	}

	return false;
}