Problem Statement
One of our Linux VPS customers was unable to send emails through the PHPMailer script with Gmail's authentication.
Solution
After some investigation, we could fix the issue by taking the following steps.
Step 1: Log in to WHM.
Step 2: Navigate to ConfigServer Security & Firewall.
Step 3: Click on Firewall Configuration.

Step 4: Locate the SMTP_Block option in WHM and toggle it to OFF to allow SMTP connections.

Step 5: Click on the Change button.
