Apply conditional access to restrict emails in mail clients (gmail or native)

Hi All,

We have corporate emails from Google and we have Intunes to manage our endpoints, now the challenge is how can we apply app policy and conditional access to allow users use only one application (outlook) to access their company e-mails and all other applications for mail access should be blocked.

Please note that we have emails from Gsuit.

I have already tried creating app protection with outlook as target app and CA, but it is not working.