Hi,

This error indicates that you're using a Gmail account with two-factor authentication (2FA) enabled. Regular passwords won't work in this scenario because Odoo can't authenticate through the interactive login process required by 2FA.

1. Log in to your Google Account: Go to Google account login.
2. Navigate to Security: Click on "Security" in the left navigation panel.
3. Manage Your Google Account: Under "Sign-in & security," click on "Sign in with Google."
4. Enable App Passwords (if not already enabled): If you haven't used app passwords before, you might need to enable them first. Look for the "App Passwords" section and click on "Turn on 2-step verification" if it's not already enabled.
5. Select App and Device: Choose "Select app" and pick "Other (Custom name)." You can enter "Odoo" as the custom name for better identification.
6. Generate Password: Select a device from the dropdown (or add a new one if needed) and click "Generate."
7. Copy the Password: Google will display a 16-character password. Copy this password securely.

Configure Odoo with the Application-Specific Password:

1. Go to Odoo Configuration: In your Odoo instance, navigate to the configuration settings for outgoing mail servers.
2. Enter Credentials: Update the username and password fields with your Gmail address and the application-specific password you just created, respectively.
3. Save and Test: Save the configuration and test the connection. You should be able to send emails successfully now.

By following these steps, you should be able to resolve the error and send emails from Odoo using your Gmail account with 2FA enabled.

Please Refer this link for your refernce https://youtube.com/watch?v=ax9GCts67Ww

Hope this helps!