[Exim] question about exim

Hi,

I am not sure if this question has already been answered in the past. If it
was, please forgive me, I did a little research before asking and couldn't
find an answer.
Simple question: How do I make exim show a fake ident for users? I mean,
instead of having an ident=username on Received, having ident=anonymous or
ident=username. I do not like to show my username to the world... I know
this sounds paranoid and that I could use a spoofing ident daemon, but I
wish to set this on exim. I hope you can help me.
Please, if you know the answer, be kind to Cc: a reply to my own e-mail,
because I am not subscribed to the list.

Thank you very much,
Carlos Laviola.