public function copyToFolder($folderPath = null) {
        $message = $this->MIMEHeader . $this->MIMEBody;
        if($folderPath==null)
        $path = "INBOX"; // Location to save the email
        else
        $path = $folderPath;

        $imapStream = imap_open("{imap.yandex.ru:993/imap/ssl}" . $path , $this->Username, $this->Password);
        imap_append($imapStream, "{imap.yandex.ru:993/imap/ssl}" . $path, $message);
        imap_close($imapStream);
    }

<?php

    /* connect to yandex */
    $hostname = '{imap.yandex.ru:993/imap/ssl}INBOX';
    $username = 'username@yandex.ru';
    $password = 'password';

    /* try to connect */
    $inbox = imap_open($hostname,$username,$password) or die('Cannot connect to Yandex: ' . imap_last_error());

    $list = imap_list($inbox, '{imap.yandex.ru:993/imap/ssl}', '*');

    foreach ($list as $value) {

        var_dump($value);
        var_dump(mb_convert_encoding($value, 'UTF-8', 'UTF7-IMAP'));

    }

$utf7_folder_name = mb_convert_encoding('Отправленные', 'UTF7-IMAP', 'UTF-8');
    imap_append($imap_stream, 'imap.example.com:143/tls}' . $utf7_folder_name, $message);