[exim] dspam and exim

I have a little problem with email addresses as -_-@example.com with
exim/dspam. (-_-@example.com is a valid email address)
I have posted this on the exim and dspam lists..

I have below
------------------------------
dspam_router_trainer:
   no_verify
   condition   = "${if and { \
                            {!def:h_X-Spam-Flag:} \
                            {!def:h_X-DSPAM-Check:} \
                            {!eq {$received_protocol}{local}} \
                            { <= {$message_size}{2048k}} \
                       {1}{0} \
                   }"
   headers_add = "X-DSPAM-Check: by $primary_hostname on $tod_full"
   driver      = accept
   transport   = dspam_spamcheck
---------------------------------------------
dspam_spamcheck:
  driver             = pipe
  command            = "dspam --mode=notrain --deliver=innocent,spam --user 
spam -f '$sender_address' -bm $local_part@$domain"
  home_directory     = "/tmp"
  current_directory  = "/tmp"
  user               = Debian-exim
  group              = mail
  log_output         = true
  return_fail_output = true
  return_path_add    = false
  message_prefix     =
  message_suffix     =
------------------------
dspam.conf

TrustedDeliveryAgent "/usr/sbin/exim4"

--------------------------------


what happens is exim passes this to dspam as:

dspam --mode=notrain --deliver=innocent,spam --user spam -f
user@??? -bm -_-@example.com

which turns when dspam reinjects in:

/usr/sbin/exim4 -f user@??? -bm -_-@example.com

and it thinks the -_- is an option.

I have tried quoting the command but doesn't seem to work

command            = "dspam --mode=notrain --deliver=innocent,spam --user 
spam -f '$sender_address' -bm \"$local_part@$domain\""

but it ignores the \"'s

Anyone help?

Thanks
Craig