The Wikileaks affair has sometimes given the impression that so-called secrets are not secret at all. I very much doubt that the average US diplomat believes that marking her or his ‘cables’ as secret means that they will be shrouded in confidentiality. But then here in UK, senders of inappropriate emails, even within companies, appear to do so under the delusion that their stuff will never leak out into the wider world. That is just idiotic.
When I was a public servant,both abroad and at home, I assumed that someone somewhere had access to my emails, and I drafted stuff accordingly. I made sure, for example, that nothing I wrote contained terms that might be triggers or sensitive keywords; not because I feared ‘opponents’ picking them up, but rather, so-called ‘friends’. If in any sort of doubt, assume the worst and write accordingly, even if it makes you sound rather formal.