Why Am I Getting 'SMTP Error: Could Not Authenticate' When Using PHPMailer with Gmail?

Authentication Error in PHPMailer: "SMTP Error: Could not authenticate"

When utilizing PHPMailer to send emails via Gmail, the "SMTP Error: Could not authenticate" message may arise. This error indicates that PHPMailer is experiencing difficulty authenticating with Gmail's SMTP server, preventing email delivery.

Root Cause and Solution:

The underlying reason for this error is typically related to the user's Google account security settings. Gmail has implemented enhanced security measures to safeguard accounts, which may interfere with the less secure authentication mechanisms used by PHPMailer.

To resolve this issue, it is necessary to disable the "Allow less secure apps" setting within Gmail account settings. This setting, found under "Sign-in & Security," allows third-party applications to access Gmail accounts with less sophisticated authentication methods. By disabling this setting and using more secure authentication methods, the issue with PHPMailer can be resolved.

Alternatively, you can generate an "App Password" for the specific email address used in your PHPMailer script. App passwords are designed to replace insecure, less secure app access. Once created, you can use the app password instead of your regular Gmail password in your PHPMailer script, providing additional security while maintaining functionality.

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