Sending emails from PHPMailer using proxies IP addresses

Question

I need to send emails from PHPMailer using proxies IP addresses, I know that to do so, I need to use the fsockopen function so I can conect to the SMTP account, I also know that if I have to connect to the proxy I have to use the fsockopen function again. But using it fsockopen inside another fsockopen is not doable.

I have transparent proxy and require no authentication. I need to send this to a distant SMTP server of an external Email Service Provider.

The code I have tried :

<?php

    //SMTP params
    $server      = 'smtp.espdomain.com';
    $server_port = '25';
    $username = 'smtp_login';
    $password = 'smtp_pass';

    //Proxy
    $proxy      = '1.1.1.1';
    $proxy_port = 1111;

    //Open connection
    $socket = fsockopen($proxy, $proxy_port);

    //Send command to proxy
    fputs($socket, "CONNECT $server:$server_port HTTP/1.0\r\nHost: $proxy\r\n\r\n");
    fgets($socket, 334);

    //SMTP authorization  
    fputs($socket, "AUTH LOGIN\r\n");
    fgets($socket, 334);

    fputs($socket, base64_encode($username)."\r\n");
    fgets($socket, 334);

    fputs($socket, base64_encode($password)."\r\n");
    $output = fgets($socket, 235);

    fputs($socket, "HELO $server \r\n"); 
    $output = fgets($socket, 515);

?>

And it's not work i'm not sure why?

Could socat commandes help in this situation or is there any solution or alternative solution to do this?

Thank you in advance.