Hi  Lawrence,

Google no longer supports the use of third-party apps or devices which ask you to sign in to your Google Account using only your username and password. So enabling Less Secure Apps also disabled 

All you need  to do is create an App Password and  replace your password with the app-generated password in the Outgoing Mail Server

Check:-

https://www.odoo.com/forum/help-1/how-to-connect-odoo-to-google-smtp-without-enabling-the-less-secure-apps-access-205557#answer-205558


Hope it helps,
Kiran K