[exim] Adding missing Message-Id header for Outlook 2003 (AU…

Is there any way I can reliably add a Message-Id header to outgoing mails
(my Outlook -> my Exim [HERE]-> internet relays) for Outlook 2003
"compatibility"?

I can generate any crap to insert into the header but I think Message-Id
needs to be unique in a way that I cannot work out how to generate it.
I've just been fighting with broken References and In-Reply-To mails in
a message forum so I would like to do it properly and not cause myself
more problems in the future by generating non-unique Ids.

I guess what I need is.. some extra-long including-microseconds time
stamp that I can attain from in the Exim config file, base64 encode it
or something for simple obfuscation, which I can then prepend to the
hostname of the sending machine?

--
Matt Sealey <matt@???>
Manager, Genesi, Developer Relations