Exim pipe outgoing emails not working

Hello,

I would like to pipe all emails Exim sends through a Python script. This script will keep a database of sending behavior, and suspends outgoing email for some domains in case of abuse, using WHM API.

I haven't coded such script yet, as I'm still not able to send emails from Exim through my script.

I have done this in Exim Configuration Manager > Advanced Editor:

Code:

Section: ROUTESTART
outgoing_processor:
  driver    = accept
  condition = ${lookup {$sender_address_domain} \
    lsearch {/etc/localdomains} {yes}}
  transport = outgoing_script
  unseen

Section: TRANSPORTSTART
outgoing_script:
  driver  = pipe
  command =  /usr/bin/tee -a /root/exim_spam_filter/outgoing.log

I'm using tee just to save the pipe output to a file, however it's not working. Emails are being delivered, but the pipe command is not being executed.

Did I miss something?