[exim] User Variable Passing - Cpanel Exim

Greetings,

I am trying to get the $local_part replaced with the information that
is passed by user in that section, so it can grab the actual owner of
the domain that the emails is intended for virtual users. However, I
could not get it to work if I replaced the $local_part with $user, so I
need some help here to get the owner of the domain to be passed for the
transport_filter.

virtual_sa_userdelivery:
driver = pipe
command = /usr/sbin/sendmail -bS
use_bsmtp = true
transport_filter = "/usr/bin/spamc -u $local_part@$primary_hostname"
user = "${lookup{$domain}lsearch* {/etc/userdomains}{$value}}"
group = mail
log_output = true
current_directory = "/tmp"
home_directory = "/tmp"
return_fail_output = true
return_path_add = false
message_prefix =
message_suffix =
timeout_defer = true
transport_filter_timeout = 5m
temp_errors = 2

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Best regards,
 Russell 'Elik' Rademacher                    mailto:elik@micfo.com
 Micfo, LLC
 Senior System Admin/Tech Manager