On Thu, 2025-03-27 at 09:15 +1100, Stephen Morris wrote:
With sensitive mails in Outlook, if you forward the mail Outlook retains the mail headers in the forwarded mail and honours the headers.
I'd expect that. Forward generally means pass it along as-it-is (that's if you pass it along as an attachment). If it just creates a new email with the original message pasted into it, I wouldn't know what to expect it to do with the headers, though ignoring them springs to mind as the most obvious behaviour.
Replying to an email is another matter. Only the headers pertinent to maintaining a thread would carry over, and any other headers that ought to, too. All the ones that shouldn't, are not (such as all the servers the original past through before you got it).
Since putting sensitivity headers into a message is being done by a plug-in with Evolution, the main program doesn't know anything about them, so ignores them.