How To Automatically Delete NON CRM Related Emails

How To Automatically Delete NON CRM Related Emails

is there a way to set up a email filter that automatically deletes email that is not Sent or Received from a CRM contact.

I can see that its possible to set up single filters on a contact by contact basis - by directly matching on a specific email address  -- but this is not practical with 100's of contacts -- plus the maintenance of this would be dreadful.

We only want to store CRM related emails in CRM else we would soon run out of "free" email storage due to the large size and number of other NON related CRM email.

I note that deleting all the emails from zoho mail also then deletes the CRM linked emails too, hence the need to only delete non CRM emails.