Re: [Nmh-workers] Domain Leakage Despite -messageid random.

[Ken Hornstein]

>What if the recipient wants to refer back to that seventh JPEG of nine?

They would probably say, "Oh, it's the one with the white cat making a
funny face".  I mean, I understand WHY that header exists, I just don't
think that it is ever used that way ... WITH the exception of text/html
parts referring to included images for rendering.  I'm trying to think of
people who would a) refer to a particular part using a Content-ID header
and b) are NOT on this mailing list.

>I had a shufty at emails here.  Ignoring those from nmh, I found
>Content-ID in the email's headers of other MUAs.  Pine was one, and
>Microsoft do it too, on occasion.

I was curious about pine, so I looked at that.  It does generate them,
but you can turn that off.  The comments are:

            /*
             * If requested, strip Content-ID headers that don't look like they
             * are needed. Microsoft's Outlook XP has a bug that causes it to
             * not show that there is an attachment when there is a Content-ID
             * header present on that attachment.
             *

The same applies to Alpine.  It looks like those are only generated for
"attachments", rather than every MIME part.

>BTW, Paul Fox, hi Paul, sent some, with nmh I presume, where one "host"
>was shorter than the other, e.g.
>
>    Content-ID: <address@hidden>
>    Message-Id: <address@hidden>

I suspect the one was created by nmh, the other created by Paul's first-hop
MTA (-nomsgid is the default for send).

AFAICT, Content-ID is only required for a message/external-body type (hm,
we MAY not get that right).

--Ken