Adding custom headers to exim4 - email

Question

Im trying to add custom headers to my Exim4 config for all my emails to show up in CloudWatch. To get it working i updated the config with below:
.ifdef DCconfig_smarthost DCconfig_satellite
# configtype=smarthost or configtype=satellite
#
# Send all non-local mail to a single other machine (smarthost).
#
# This means _ALL_ non-local mail goes to the smarthost. This will most
# probably not do what you want for domains that are listed in
# relay_domains. The most typical use for relay_domains is to control
# relaying for incoming e-mail on secondary MX hosts. In that case,
# it doesn't make sense to send the mail to the smarthost since the
# smarthost will probably send the message right back here, causing a
# loop.
#
# If you want to use a smarthost while being secondary MX for some
# domains, you'll need to copy the dnslookup_relay_to_domains router
# here so that mail to relay_domains is handled separately.
smarthost:
debug_print = "R: smarthost for $local_part#$domain"
driver = manualroute
headers_add = X-SES-CONFIGURATION-SET: CloudWatch
headers_add = X-SES-MESSAGE-TAGS: customer=senet, application=twentyfour
domains = ! +local_domains
transport = remote_smtp_smarthost
route_list = * DCsmarthost byname
host_find_failed = ignore
same_domain_copy_routing = yes
no_more
.endif
This actually works well where i updated the debug message on the router and while sending emails from the CLI that specific message was shown.
When i check the exim config exim -bP config i see that also there the info is set properly:
begin routers
smarthost:
debug_print = "R: smarthost for $local_part#$domain"
driver = manualroute
headers_add = X-SES-CONFIGURATION-SET: CloudWatch
headers_add = X-SES-MESSAGE-TAGS: customer=senet, application=twentyfour
domains = ! +local_domains
transport = remote_smtp_smarthost
route_list = * email-smtp.eu-central-1.amazonaws.com:587 byname
host_find_failed = ignore
same_domain_copy_routing = yes
no_more
COND_LOCAL_SUBMITTER = "${if match_ip{$sender_host_address}{:#[]}{1}{0}}"
The only problem is that i don't see any of these 2 headers in my actual email.
Thanks in advance,
Best,
Pim