For G Suite.
How to restrict access for mail clients that use POP/IMAP/Sync?
In order to restrict the access to POP/IMAP from a mail client or to restrict the access to Google Sync from a smart device, set up the setting on the G Suite Admin Console.
Please refer to the G Suite Support site shown below.
Settings for IMAP and POP access
G Suite mobile management /settings
This settings is the G Suite feature.
For further details, please contact the G Suite.