[Exim] where its being delivered to...

Hi,

I am using Exim on a Virtual Hosting site. I have control of my Exim
filter file, and would like to handle mail differently per user (pre-sort,
spam filter, etc).

Is there any variable that tells me which mailbox the message is going to
be delivered to?
Right now, mail for 'foo@???' goes to this mailbox:
/home/user/mail/bar.com/foo/inbox

Basically, I want to know if theres anything (in Exim filtering variables,
or the headers) that tells me that user 'foo' is getting the mail.
The 'To' header may be an email forwarder, or a mailing list address,
bcc'd, etc., so I cannot dissect that to find the user. (or can i?)

I'm sorry if this is a really dumb question -- I'm just new to Exim and
need some guidance.

Thanks in advance for any help,
Brandon