Would it be acceptable for the third-party provider (whether Mozilla or not) that you're paying email and matrix hosting services to run automated content scanners on the email and chat server to detect known malware and child pornography content signatures?

A lot of people take for granted that "I pay you money" implies "I have the right to use your service without you having any right to inspect my usage of your service", and it'd be useful to know your views on that.