To learn how to use Google/Gmail/GSuite as your SMTP provider, read:

Important: After turning on 2-Factor Authentication, if you do not see the option to set "App Passwords" on the Security page, click on 2-Factor Authentication and it will take you to another page where you can set the "App Passwords."

Important: if you are using Google Workspace as your SMTP Provider:

  1. Setup Route outgoing SMTP relay messages through Google 
  2. Allow Less Secure Apps in Google Workspace Admin and the individual Google email account

Important: you can also send email from Google Workspace Alias addresses.

Also, learn why you can't use a free email address as an SMTP provider: