IRIS 1000002331 - Gmail Settings
Less secure apps & your Google Account

To help keep your account secure, starting May 30, 2022, Google will no longer support the use of third-party apps or devices which ask you to sign in to your Google Account using only your username and password.
Google might block Pantheon which is trying to sign in to your account from it.
In order to use Google (Gmail) for sending and receiving emails from and into Pantheon you must first Turn on 2-Step Verification and then generate a 16-digit passcode that gives a non-Google app or device permission to access your Google Account - Sign in with App Passwords.
, for more info click Google Seetings.