[exim] Try to write an acl /acl_smtp_data to read header con…

Dear all,

I try to write an acl in the section acl_smtp_data.
The purpose is to catch an entry in a specific spam header
:UNPARSEABLE_RELAY. If exim find that entry it should produce a log entry
like "unparseable entry found".
In did it like that
warn condition = ${if match{h_x-spam-status:}{"UNPARSEABLE_RELAY"}}
message= unparseable entry found!!

With no succuess. Is it possible to catch header entries within
all_smtp_data?

Greetings
Daniel