MailboxDirectory::countMessagesSyncDirs

static function countMessagesSyncDirs($mailboxId)
{
	$counter = MailboxDirectoryTable::getList([
		'filter'  => [
			'=MAILBOX_ID'  => $mailboxId,
			'=IS_SYNC'     => MailboxDirectoryTable::ACTIVE,
			'=IS_DISABLED' => MailboxDirectoryTable::INACTIVE
		],
		'select'  => ['CNT'],
		'runtime' => [
			new ExpressionField('CNT', 'SUM(%s)', 'MESSAGE_COUNT'),
		]
	])->fetch();

	return (int)$counter['CNT'];
}