I'm using AIP to apply a "Confidential" label to certain emails/documents. I'm using the classic client, not the new Unified Labeling.
In my org, confidential documents shouldn't be shared outside the business, with the exception of our (non-federated & using GSUITE) parent company.
I've set the Confidential label to auto apply co-owner permissions for the parent co's domain.
The problem I have is when I send a confidential file to the parent co, they receive the "XYZ has sent you a protected message" then have to authenticate to open the email.
How do I stop them receiving this message? I essentially want to treat the parent co like any member inside my domain, they receive the email & open it as normal, no "protected message" email, no buttons to click etc.