[Users] Message-ID

[RW]

On Wed, 30 Jan 2013 19:51:58 -0500
Rich Pieri wrote:

> On Tue, 29 Jan 2013 11:31:30 +0100
> Andreas Meyer <anmeyer at anup.de> wrote:
> 
> > ok, but the MTA would create a Message-ID only if CM wouldn't create
> > one. And as you said in other mail, creating such an ID is
> > obligatory in case of IMAP. So no chance to let the MTA create one.
> 
> Don't count on it. There are plenty of reasons (some good, some bad)
> for a MTA to rewrite existing Message-ID fields, such as a private
> network using an someone else's domain name. Regardless of the
> validity of that practice (it's ill advised but not prohibited), the
> "illegal" domain name must not be exposed to the public network. This
> entails stripping internal Received headers and rewriting everything
> else to masquerade the domain parts.
> 
> Practices like these are one of the reasons why mail handling
> unofficially adopted Usenet style References headers. References
> headers were formally rolled into mail handling specs with RFC 2822. I
> should hope that CM prefers to use References over In-Reply-To and
> Message-ID.

Reference headers make it possible to keep a thread together when
there are missing messages, but they don't avoid the need for
Message-IDs.