removing header of originating smtp from relayed mail

[Stéphane MERLE]

Hi,

I am using a postfix as relay for email sent from an hoster that close 
the port 25, so I send the mail to the relayer through the 10025 port.
but the IP of the originating server appear in the header of the mail 
and I would like to remove it :

source server  ---10025---> relayer ---25---> FAI

just showing the relayer ip and hostname, I have access to both config 
files, is this possible ?

Thanks for your help.

Stéphane
PS : sorry for my english