[Nmh-workers] Message-IDs and Content-IDs

[David Levine]

I've been thinking more about Message-IDs.  The way nmh,
sendmail, and Fedora configure things by default, the host
part is worthless, but I expect that's common in these
halcyon days of NAT.  And on some hosts, I want the real
hostname to be masked, esp. when using a masqueraded From:
address.  (It can't be masked in Received headers, but I'll
do what I can.)

"Host part" is pseudo, it's after the @ and can include most
ASCII printable characters.

So I'm thinking of generating a Message-ID based on a
MAC address.  Something of the form:
address@hidden, where md is the sha1 hash of the pid,
timestamp, and MAC address.  That would take care of the
worthless and unmasked host part.

And as a bonus, I could easily determine if a message with a
particular Message-ID originated from my machine.

One downside is that there's no portable way to retrieve
MAC addresses.  (In other words, I would just do it on Linux
but would incorporate contributions for other platforms.)
But Message-IDs are supposed to be globally unique, so I
don't think there are other easy alternatives.

We had talked about allowing the host part to be configured
by the user (identname/idname), this seems like a good place
to include that as well.

Content-ID has a very similar format to Message-ID, it just
adds the part number.  I think it should be handled the same
way.

Comments?

David