[exim] S= tag inside exim_reject.log on rejects after data

Hi all

I notice that with my installation of exim (4.62 on Gentoo linux) that
the rejects that take place after the data phase does not include a S=
tag in the reject line to indicate what the size of the message was.

An example may be in order, I found this line (modified to hide real hosts):

2007-03-22 03:10:34 1HUBp4-0003l3-2b H=smtp101.some.isp [1.2.3.4]
F=<some@???> rejected after DATA: This message contains
malformed MIME (demime acl condition: base64 line contains illegal
character).

Now, since this happened after the data phase of the smtp negotiation
the size of the message has to be known not true? Basically, the entire
message has been transfered and now it's being rejected. I'm busy
performing some log analysis and one of the questions that I'm posing
and trying to answer is "how much message data do we receive over the
wire that we simply throw away?".

Is it possible to have exim add the S=4321 tag indicating the size to
the message logs in some configuration way, or do I need to add an entry
to the data acl to log this explicitly? I'd prefer to not have to
generate a seperate entry as that would complicate the parsing process
even more than what it is currently.

Thanks,

Jaco