[Exim] exim transport_filter problems

Hello,

I'm trying to run all incoming mail through bogofilter via the
virtual_userdelivery transport below. A X-Bogocity spam header is added
to each message, telling whether or not it's spam. (I will be building
word lists manually with cron jobs going through designated imap spam
folders for certain knowledgeable users)

Anyway... here is the transport it's sending through:
##############################################################
virtual_userdelivery:
driver = appendfile
file =
"${extract{5}{:}{${lookup{${lookup{$domain}lsearch*{/etc/userdomains}{$value}}}lsearch{/etc/passwd}{$value}}}}/mail/${domain}/${local_part}/inbox"
quota = "${if
exists{${extract{5}{:}{${lookup{${lookup{$domain}lsearch*{/etc/userdomains}{$value}}}lsearch{/etc/passwd}{$value}}}}/etc/${domain}/quota}
{${lookup{$local_part}lsearch*{${extract{5}{:}{${lookup{${lookup{$domain}lsearch*{/etc/userdomains}{$value}}}lsearch{/etc/passwd}{$value}}}}/etc/${domain}/quota}{$value}}}
{}}"
delivery_date_add
envelope_to_add
return_path_add
user = "${lookup{$domain}lsearch* {/etc/userdomains}{$value}}"
group = mail
transport_filter = "/usr/local/bin/bogofilter p -u -e -d
/root/.bogofilter"
mode = 0660
##############################################################

All bogofilter -p does is use the word list in /root/.bogofilter and
append 1 header to the mail:
X-Bogocity: Yes


And here's a few errors that show up in my /var/log/exim_mainlog
######################################
2002-12-17 14:36:52 18ONP7-0002ue-00 == webmaster@???
T=virtual_userdelivery defer (32): Broken pipe: error while writing to
/home/thedomai/mail/thedomain.com/webmaster/inbox
2002-12-17 14:37:07 18ONWd-00048I-00 == webmaster@???
T=virtual_userdelivery defer (-25): filter process failure -11 while
writing to /home/thedomai/mail/thedomain.com/webmaster/inbox
2002-12-17 16:27:40 18OPFb-00009G-00 == webmaster@???
T=virtual_userdelivery defer (-25): filter process failure 2 while
writing to /home/thedomai/mail/thedomain.com/webmaster/inbox
2002-12-17 16:25:32 18OPDX-0008NN-00 == webmaster@???
T=virtual_userdelivery defer (-25): filter process failure 2 while
writing to /home/thedomai/mail/thedomain.com/webmaster/inbox
######################################

Here's the file its complaining about:
-rw-rw----    1 thedomai mail        29834 Dec 17 14:34
/home/thedomai/mail/thedomain.com/webmaster/inbox

So, I have two questions:
Is there anything totall obvious that you can see I'm doing wrong?
Is there a better way I could be doing this?

I would do it via procmail, but this is a virtual host, and not every
user has their own home directory where a .procmailrc file could sit.

Thanks in advance for any and all help,
Brandon Martus