On 06/08/2017 06:52 PM, Nicholas D Steeves wrote:
I'd prefer not to, because Message-ID reveals what I consider private information (IP address or client hostname) to an unbounded audience, and I believe that this is a greater privacy violation than the lintian warning against downloading a hyperlinked image in local [...]
That depends on the software that generated the message (e.g., Thunderbird seems to do uuid@domain, so avoids the privacy issue—at least it reveals less than the From header), but where it does you could just redact the hostname (or entire domain). That'd still preserve the ability to reference an individual message.
Message-Id: <localpart@...> and Message-Id: <localpart@REDACTED> are both pretty clear what you're doing.