You can use BetterCloud for G Suite's policies to create email settings that are right for your domain. POP and IMAP protocols allow someone to download messages from Gmail's servers onto her desktop or mobile mail client; by managing these settings, you can allow your users to be able to access mail with a non-cloud based program.
Create a Policy
Navigate to Email Tools and select IMAP/POP
Click Create IMAP/POP policy
IMAP/POP in the Admin Console
Alternatively, you can disable IMAP/POP on a domain wide level in the Google Admin Console: