[exim] Exim.conf and tainted data

I will admit reading the tainted/detainting documentation quite a few
times, and I'm just not figuring out how to make it all work. I've used
the same exim.conf for quite some time, and I would rather figure it out
before breaking it completely. The only parts I am seeing that may break
are the following:

routers:

local_aliases:
driver = redirect
allow_defer
allow_fail
domains = lsearch;/etc/exim/config/local.domains
data = ${lookup{$local_part}lsearch{/etc/exim/config/$domain/local.aliases}}
file_transport = address_file
pipe_transport = address_pipe
retry_use_local_part
cannot_route_message = Unknown user
no_more


transports:

local_delivery:
  driver = appendfile
  directory = /home/$local_part/.maildir
  maildir_format                                                                                        
  delivery_date_add                                                                                     
  envelope_to_add                                                                                       
  return_path_add

Can anyone take a moment to help me debug this? Unfortunately I don't
believe the Gentoo ebuild has added the new allow_insecure_tainted_data
compile time option as a stopgap.

Thanks a ton for your help.