[Exim] condition in acl_smtp_data

Hello,

check_message:
require verify = header_syntax
warn message = X-Authenticated: $authenticated_id
condition = ${if !def:h_X-Authenticated: {yes}{no}}
authenticated = *
accept

The condition only apply to warn message, or to the whole require verify?

I would like avoid adding duplicated X- headers, and also would not
like adding host specific headers like X-Auth-hostname:

Seems like this condition works, but I'm not sure it does what I want.