Verify Email using SMTP protocol doesn't work on Cloud Ubuntu VM Instance

Question

I wish to create my own Signup System and I'm having difficulty with Email Existence Verification. I'm using this following PHP script posted on https://www.mywebcode.com/verify-email-address-check-if-real-exists-domain-php/ as verify_email_library.inc.php in my website. This script is able to work and check entered email existence perfectly on my localhost Xampp Server. But when I upload my website on my Google VM Instance Ubuntu , this script doesn't work in any way. Can someone let me know what I will have to configure or install on my VM Instance . Thanks

verify_email.php:

<?php
    include_once "verify_email_library.inc.php";
    $vmail = new VerifyEmail();
    $vmail->Debug= TRUE;
    $vmail->Debugoutput= "html";
    echo "<p>".($vmail->check("EMAIL@gmail.com") ? "Email Exists" : "Email doesn't Exists");
?>

The error I'm getting:

gmail-smtp-in.l.google.com:Connection timed out
alt1.gmail-smtp-in.l.google.com:Connection timed out
alt2.gmail-smtp-in.l.google.com:Connection timed out
alt3.gmail-smtp-in.l.google.com:Connection timed out
alt4.gmail-smtp-in.l.google.com:Connection timed out
All connection fails
Email doesn't Exists

Answer 1

As per the google cloud compute documentation :

By default, Google Compute Engine allows outbound connections on all ports but port 25, which is blocked because of the risk of abuse. All other ports are open, including ports 587 and 465.

You will need to use a different hosting service, or use a proxy/tunnel/vpn if you wish to make SMTP connections.