Can you really tell it's rude without looking at the content of the message? It might be odd, and it's likely to be unnecessary and, yes, rude; but I can imagin

Can you really tell it's rude without looking at the content of the message? It might be odd, and it's likely to be unnecessary and, yes, rude; but I can imagine situations where I might be contacted unexpectedly with a GPG-encrypted message for a good reason.