[Exim] Preserve header files

Hi,

I would like some feedback about the idea of being able to retain the header
files of messages for a period of time (about a week), essentially for the
purposes of auditing.

I'm frequently asked if I can provide information about messages that have
gone through our system in cases of reported abuse, and the answer is
typically: "Yes if I had the headers, but I don't".

I don't think that increasing log verbosity or preserving msglogs would
provide the desired information.

Does anyone think this is a particularly bad idea?

Does anyone have any bright ideas on how to achieve this?
I'm thinking along the lines of hardlinking the header files into a
different directory (dir name based upon date).

Cheers,
Matt.