Gmail Less Secure Apps

1. Open your Gmail Account 2. Click "Apps" at the upper right (9 dots) > Click Account 3. Click Sign-in & Security > Scroll down Click "Enable Less Secure Apps" 4. If you didn't see "Enable Less Secure Apps", request to your Super Administrator to turn-on "Less Secure Apps" in the Admin Console Reference for Gmail Message Header link: (Super Administrator account)
See other articles in G Suite Support, Troubleshooting.