Software⏱️ 2 min read📅 2026-05-31

How to Fix: Gmail Error :The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required

Learn how to fix: Gmail Error :The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required.

Quick Answer: Try checking your system settings or restarting.

To resolve the Gmail SMTP authentication error, you need to enable Less secure app access or generate an app password for your Gmail account on the Google Account settings page.

🔍 Why This Happens

  • [Cause]

🔧 Proven Troubleshooting Steps

Method 1: Enable Less Secure App Access

  1. Step 1: Go to your Google Account settings page.
  2. Step 2: Scroll down to the Less secure app access section and toggle the switch to enable it.

Method 2: Generate an App Password

  1. Step 1: Go to your Google Account settings page.
  2. Step 2: Click on Security and then select App password.
  3. Step 3: You will be asked to select how you want to use the app password. Choose Mail, and then click on Create.

🎯 Final Words

By following these steps, you should be able to resolve the Gmail SMTP authentication error and send emails successfully from your production server.

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