PHPMailer "Connection refused (111)" Error Despite Outbound Ports Being Open

PHPMailer "Connection refused (111)" Error Despite Outbound Ports Being Open

Hello everyone,

I'm trying to send emails via Zoho SMTP using PHPMailer on my shared hosting environment. I've tried both port 465 (ssl) and 587 (tls), and I even added SMTPOptions to bypass SSL verification just in case it was an SSL certificate issue. However, the connection drops instantly. 

Here is my current configuration:

$mail->isSMTP();
$mail->Host       = 'smtppro.zoho.com';
$mail->SMTPAuth   = true; 
$mail->SMTPOptions = array(
    'ssl' => array(
        'verify_peer' => false,
        'verify_peer_name' => false,
        'allow_self_signed' => true
    )
);
$mail->Username   = '<myemail>';
$mail->Password   = '<mypassword>'; // application password
$mail->SMTPSecure = 'ssl';
$mail->Port       = 465;
$mail->CharSet    = 'UTF-8'; 

The debug output (SMTPDebug = 2) is very short, meaning it fails at the TCP level before any SMTP negotiation happens:
"SMTP ERROR: Failed to connect to server: Connection refused (111) SMTP Error: Could not connect to SMTP host. Failed to connect to server"

My hosting provider insists that outbound ports 465 and 587 are open. My questions are:
1. Could this be caused by SELinux blocking network connections for the web server (e.g., httpd_can_network_connect = 0)?
2. Is it possible that the server's IPv6 configuration is broken, and PHPMailer is trying to resolve Zoho via IPv6?
3. How can I definitively prove to the hosting provider whether this is an OS/Firewall issue on their end?

Thanks in advance for your insights!

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