it would be nice to specify email to a specific case/item...

Mr smith may be 1 person, but we handle multiple cases on his behalf... he emails pictures of an accident to us but also emails in his car registration number for another case... the two emails show together even though they have no relevance to one another

a final reason for this being important is data protection... our clients may have a medical related legal case with us that our guys on the delayed flights team should not be able to see... 

while i can set record permissions in the custom module, we can't control the flow of email, therefore communication with the client is public regardless of the content.