PHP imap not append big mail - php

Question

I am handling imap in php via socket. Everything works perfect. I build mail swift object, then convert it to string and send to imap with append command, it works, I get OK [APPENDUID 1 4497] (Success), but if I attach file greater than about 3kb - imap server responds me nothing, and the mail doesn't append! What is the problem? May be I should make append something like part by part? I mean cut mail body for several parts and make several fwrite()?
These are several parts of my code. But I think problem is not in the code, but in some common imap stuff:
/**
* #param string $command
* #param string $successPattern
* #param bool $withCounter
* #return false|string
*/
protected function sendCommand($command, $successPattern = '', $withCounter = true)
{
$counter = $withCounter ? "{$this->commandHash}{$this->commandCounter} " : "";
$successPattern = !$successPattern ? $counter . 'OK' : $successPattern;
fwrite($this->stream, "{$counter}{$command}\r\n");
$this->commandCounter++;
$previousLine = '';
$buf = '';
$time = time();
while ((time() - $time) < $this->timeOut) {
$newLine = fread($this->stream, 4096);
if(!strlen($newLine)) continue;
$buf .= $newLine;
file_put_contents("/LOG2.txt", $newLine, FILE_APPEND);
if (strripos($previousLine.$newLine, $successPattern) !== FALSE){
$this->responseContainer->setLastResponseText($buf);
return $buf;
}
if (strripos($previousLine.$newLine, $this->commandHash . ($this->commandCounter - 1) . ' NO') !== FALSE
|| strripos($previousLine.$newLine, $this->commandHash . ($this->commandCounter - 1) . ' BAD') !== FALSE){
$this->responseContainer->setLastErrorText($buf);
return false;
}
$previousLine = $newLine;
}
var_dump(" Time out");
$this->responseContainer->setLastErrorText("{$command} {$counter} Time out");
return false;
}
/**
* #param $mailString
* #param string $folder
* #return false|int
*/
public function append($mailString, $folder = "INBOX")
{
if($this->sendCommand("APPEND {$folder} {".strlen($mailString)."}", "go ahead")){
$response = $this->sendCommand($mailString, '', false);
return $this->imapParser->parseAppendResult($response);
}
return false;
}
$message = new \Swift_Message();
$message->setSubject($mail->subject);
$message->setFrom($mail->from);
$message->setTo($mail->to);
$message->addPart($mail->body, 'text/html');
foreach($mail->files as $file){
$attachment = \Swift_Attachment::fromPath($file->getPath());
$attachment->setFilename($file->name.".".$file->type);
$message->attach($attachment);
}
$appendUid = $this->imapService->getCommander()->append($message->toString());
Creating stream:
/**
* #param string $host
* #param integer $port
* #return bool
*/
protected function createStream($host, $port)
{
//#todo proxy authentication
if($this->stream = #stream_socket_client("ssl://{$host}:{$port}", $errno, $errstr, $this->timeOut, STREAM_CLIENT_CONNECT, $this->context)) {
stream_set_timeout($this->stream, $this->timeOut);
return $this->stream;
}
$this->responseContainer->setLastErrorText("Failed connection to imap. Without proxy. " . $errstr);
return false;
}