[exim] howto modify received_header_text

Hello,

I would like to add a custom received_header_text as described at

http://wiki.apache.org/spamassassin/EnvelopeSenderInReceived

Which file do I edit/create to do this? I am using exim 4.50 with split
configuratin on debian.

I do not yet have a good grasp of the different configuration files, so
thank you for your patience on what is probably quite obvious to those
with more knowledge.

--
Good day, eh.
Chris