Google decided to restrict Less Secure Apps (LSAs) to access G Suite.If any non google app that access google accounts just using username and the password are called the Less Secure Apps (LSAs) .For each authentication request, Less Secure Apps have to be sent the username/password pair to the server which will allow attackers to steal the user’s credentials when connections are not secured using Transport Layer Security (TLS).

These limitations will gradually enforce starting from February to June of 2020.However last October google removed the “Enforce access to less secure apps for all users” setting from the Google Admin console.

Google blog mentioned, “This is most likely to impact users of legacy email, calendar, and contacts apps—see below for more details. We’ve also emailed your organization’s primary admin with details around this change. That email includes a list of users who are likely to be affected.”

To secure google accounts and prevent hacking attempts, google will fully and only support OAuth authentication.Google advises developers to update their apps to use OAuth 2.0 as a connection method to maintain G Suite account compatibility and provides help on how to use OAuth 2.0 to access Google APIs.

Read the blog posted by google