[exim] writing a message to log inside a router?

Hi Guys,

Is there any way to write a message to the mainlog from inside a
router? I'm working on an archiving project that archives copies of
all mail for a set of domains - I want to write some details to the
log for every message received before determining whether to save a
copy or not.

Here's what my router looks like:

archive_router:
driver = accept
condition = ${lookup{$domain}lsearch{/etc/mail/archive_domains}
{yes}{no}}
transport = archive_incoming
unseen = true

So ulitmately i'd like to write to the log before the lookup condition.

Is there anyway to do this? log_message appears to only be valid in
acls.

Cheers,
Marcus