[Users] Message-ID

[Rich Pieri]

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.

-- 
Rich P.